written by Tara Haelle

Brace yourselves: Flu season is coming! And with the coughing, fevers and aches come all the alarmist articles and blog posts on unreliable, misinformative websites questioning the flu vaccine’s safety and effectiveness. There are already some good posts out there that address some of these misconceptions about the vaccine so many love to hate (including the CDC’s own one), but none quite get around to addressing every last claim I’ve heard, and most don’t provide the citations right then and there to back up the accurate information provided.

And so I began this list last year, attempting to address every last myth about the flu vaccine I had come across and provide all the links needed to see where my information had come from. Admittedly, some of the “myths” aren’t exactly myths – they contain a morsel of truth in them – but they are misconceptions in that the morsel of truth has become twisted, misrepresented or misunderstood, and therefore important to address.

The post last year went unexpectedly, uh, viral, revealing just how much people are craving accurate information about the flu vaccine. Hopefully it convinced at least some people to get the vaccine since last season’s H1N1 strain hit young adults particularly hard. Either way, I’ve decided to update the posts for the 2014-2015 flu season. So far this year, of course, Ebola has upstaged the flu and stolen most of the headlines about a killer virus. But flu season has not really quite begun just yet, so it remains to be seen which one will dominate the media throughout the winter. What’s ironic is that the flu kills more people in one year – in the U.S. alone – than Ebola has killed ever in history worldwide.

But I’m already getting ahead of myself – I’ve bumped Ebola to #1 on this year’s list – so let’s get to it with two quick, important notes: First, for those who prefer to do their own research, I’ve provided all my sources in hyperlinks. More than half of these go directly to peer-reviewed medical research, and a fair number go to the Centers for Disease Control and Prevention or the World Health Organization.

Second, but very important: I am a science journalist but not a medical doctor or other health care professional. I’ve compiled research here to debunk common myths about the flu vaccine. You should always consult a reliable, trusted medical professional with questions that pertain specifically to you. For the CDC recommendations on the 2014-2015 flu vaccines (including information on which vaccines pregnant women, the elderly and children under 2 should *not* get), please consult the CDC flu vaccine recommendations directly. There are indeed people who should *not* get the flu vaccine.

To make it easier to navigate, I’ve listed all 31 myths at the top followed by the factual information in parentheses, which is also a link to jump to that explanation. I use “flu shot” and “flu vaccine” interchangeably to refer to any type of flu vaccine, including the nasal vaccine. For those familiar with last year’s post, although I have made a couple updates and changes throughout, the completely newly added myths are #1 through #5 and #28, #32 and #33.

Myth #1: You should fear Ebola more than the flu.

Fact: The flu poses greater risk to you than Ebola.

Myth #2: You don’t need the flu vaccine this year if you got it last year.

Fact: You need a new flu shot each year.

Myth #3: The flu shot is a “one size fits all” approach that doesn’t make sense for everyone.

Fact: You have many flu vaccine options.

Myth #4: People die from the flu shot.

Fact: There have been no confirmed deaths from the flu shot.

Myth #5: Deaths from the flu are exaggerated.

Fact: Thousands of people die from flu in a typical year.

Myth #6: The flu vaccine gives you the flu or makes you sick.

Fact: The flu shot can’t give you the flu.

Myth #7: Flu vaccines contains dangerous ingredients, such as mercury, formaldehyde and antifreeze.

Fact: Flu shot ingredients are safe.

Myth #8: Pregnant women should not get the flu shot. The flu shot can cause miscarriages. Pregnant should only get the preservative-free flu shot.

Fact: Pregnant women should get the flu shot. Fact: The flu shot reduces miscarriage risk. Fact: Pregnant women can get any inactivated flu vaccine.

Myth #9: Flu vaccines can cause Alzheimer’s disease.

Fact: There is no link between Alzheimer’s disease and the flu vaccine; flu vaccines protect older adults.

Myth #10: Pharmaceutical companies make a massive profit off flu vaccines.

Fact: They’re a tiny source of pharma profit.

Myth #11: Flu vaccines don’t work.

Fact: Flu vaccines reduce the risk of flu.

Myth #12: Flu vaccines don’t work for children.

Fact: Flu vaccines reduce children’s risk of flu.

Myth #13: Flu vaccines make it easier for people to catch pneumonia or other infectious diseases.

Fact: Flu vaccines reduce the risk of pneumonia and other illnesses.

Myth #14: Flu vaccines cause vascular or cardiovascular disorders.

Fact: Flu shots reduce the risk of heart attacks and stroke.

Myth #15: Flu vaccines can break the “blood brain barrier” of young children, hindering their development.

Fact: Flu vaccines have been found safe for children 6 months and older.

Myth #16: Flu vaccines cause narcolepsy.

Fact: The U.S. seasonal flu vaccine does not cause narcolepsy.

Myth #17: The flu vaccine weakens your body’s immune response.

Fact: The flu vaccine prepares your immune system to fight influenza.

Myth #18: The flu vaccine causes nerve disorders such as Guillain Barre syndrome.

Fact: Influenza is more likely than the flu shot to cause Guillain-Barré syndrome.

Myth #19: The flu vaccine can make you walk backwards or cause other neurological disorders.

Fact: Neurological side effects linked to flu vaccination are extremely rare (see Myth #18), but influenza can cause neurological complications.

Myth #20: Influenza isn’t that bad. Or, people recover quickly from it.

Fact: Influenza knocks most people down *hard*.

Myth #21: People don’t die from the flu unless they have another underlying condition already.

Fact: Otherwise healthy people DO die from the flu.

Myth #22: People with egg allergies cannot get the flu shot.

Fact: People with egg allergies can get a flu shot.

Myth #23: If I get the flu, antibiotics will take care of me.

Fact: Antibiotics can’t treat a viral infection.

Myth #24: The flu shot doesn’t work for me, personally, because last time I got it, I got the flu anyway.

Fact: The flu shot cannot guarantee you won’t get the flu, but it reduces your risk.

Myth #25: I never get the flu, so I don’t need the shot.

Fact: You can’t predict whether you’ll get the flu.

Myth #26: I can protect myself from the flu by eating right and washing my hands regularly.

Fact: A good diet and good hygiene alone cannot prevent the flu.

Myth #27: It’s okay if I get the flu because it will make my immune system stronger.

Fact: The flu weakens your immune system while your body is fighting it and puts others at risk.

Myth #28: If I do get the flu, I’ll just stay home so I’m not infecting others.

Fact: You can transmit the flu without showing symptoms.

Myth #29: Making a new vaccine each year only makes influenza strains stronger.

Fact: There’s no evidence flu vaccines have a major effect on virus mutations.

Myth #30: The side effects of the flu shot are worse than the flu.

Fact: The flu is worse than flu shot side effects.

Myth #31: The “stomach flu” is the flu.

Fact: The “stomach flu” is a generic term for gastrointestinal illnesses unrelated to influenza.

Myth #32: If you haven’t gotten a flu shot by November, there’s no point in getting one.

Fact: Getting the flu shot at any time during flu season will reduce your risk of getting the flu.

Myth #33: The flu vaccine causes Bell’s palsy.

Fact: The flu shot does not cause Bell’s palsy.

Myth #1: You should fear Ebola more than the flu. ( Fact: The flu poses greater risk to you than Ebola .)

Whether Ebola or the flu is worse depends on how you compare them – I’m certainly not going to claim a person should prefer Ebola to flu. But by most measures, we have far more to worry about with influenza than with Ebola. As I mentioned above, in historical and annual terms, the flu wallops Ebola in total death count. Until this year, Ebola had killed 1,590 people, according to WHO. So far this year, 3,431 people have died from Ebola, making this year’s outbreak by far the worst ever (though it has its own myths), and that’s no small thing for the thousands suffering in the west African countries of Guinea, Liberia and Sierra Leone. But that gives us 5,021 total deaths from Ebola in the history of the world.

By comparison, deaths from the flu in the U.S. alone have ranged from 3,300 to 49,000 deaths annually (more on those estimates in Myth #5). The WHO estimates a quarter to a half million people die worldwide from the flu each year, and the infamous 1918 flu epidemic killed approximately 50 million people worldwide. 50 MILLION, with an M, compared to just over 5,000 THOUSAND from Ebola. In terms of contagiousness, both flu and Ebola have an R0, or basic reproduction number (helpfully described here), of about 2. But flu is airborne and harder to contain, whereas Ebola is transmitted only through direct contact with infected bodily fluids (it’s not airborne, folks) and therefore easier to contain, relatively speaking.

Of course, measured in terms of the mortality rate, Ebola certainly beats out flu with a far, far higher risk of death once you have the disease. One of the things that makes Ebola so frightening is the mortality rate, estimated by the WHO as ranging from 25% to 90%. However, there’s a huge caveat to that mortality rate: note the list of countries who have suffered Ebola outbreaks. They are all African nations with a less developed health care system than in the U.S. or most other developed nations. You cannot compare a disease’s death rate in poorly resourced, lower-income countries in Africa to what it would be in the U.S. Ebola’s death rate in Africa still significantly exceeds the influenza death rate in Africa, so it is a more dangerous disease in Africa, but not in the U.S.

Myth #2: You don’t need the flu vaccine this year if you got it last year. ( Fact: You need a new flu shot each year .)

This is one of those less clear-cut misconceptions – not quite a myth but not quite true either. Typically, the strains included in each year’s flu vaccine change from one year to the next, based on the WHO’s educated guess on which strains are most likely to circulate. That’s why you need a new flu shot each year, to be sure your body is making antibodies for the strains most likely – the experts think – to be floating around. But this year’s strains, unusually, happen to be the same ones included in last year’s flu shot:

an A/California/7/2009 (H1N1)pdm09-like virus

an A/Texas/50/2012 (H3N2)-like virus

a B/Massachusetts/2/2012-like virus

B/Brisbane/60/2008-like virus (in the quadrivalent vaccines only)

It’s therefore a pretty reasonable question: if I got the flu shot last year, do I really need the same one again this year? The best answer is “probably.” It’s true that flu antibodies against one particular strain have the potential to last a loooooong time, at least if you had the flu. A 2008 study found that people who survived the 1918 flu pandemic still had antibodies for that specific strain decades later. But that was the flu, not the seasonal flu vaccine, stimulating the body’s antibody production (and it was only against that *one* strain, of which there are thousands).

Because it’s so rare to have the same exact strains in consecutive years’ vaccines, there isn’t enough evidence to know whether last year’s shot will protect you this year or not. We know that the flu vaccine is manufactured with the intent to protect you for only one season, and we know some vaccines’ immunity wanes (sometimes even ones that aren’t supposed to). In fact, the flu vaccine’s effectiveness has been shown to wane, particularly among older adults. On the other hand, a very recent multi-year study found similar levels of protection from both the current year’s flu vaccine and the previous year’s vaccine (but those who benefitted most from the shot were those who hadn’t had one in the past five years). So you may have some protection if you got the shot last year, but we don’t know how much and there’s no guarantee that you have any.

Myth #3: The flu shot is a “one size fits all” approach that doesn’t make sense for everyone. ( Fact: You have many flu vaccine options .)

This one couldn’t be further from the truth. While there are definitely some people who should not get any flu vaccine, most people have more options than ever before in choosing the vaccine that’s best for them. Last year, I got the trivalent injection while pregnant. This year, I got the quadrivalent live nasal vaccine, but there are potentially nine other options this year. There’s the good old-fashioned trivalent (three-strain) shot, with or without the preservative thimerosal, or an intradermal trivalent shot that goes into the skin instead of your muscle. If you’re over 65, you can get the high dose shot, and if you are concerned about egg allergies, you can get the cell-based or the recombinant flu vaccine. Or you could get the quadrivalent shot (with or without thimerosal) instead of the quadrivalent nasal vaccine. Or, if you hate needles and don’t want a live vaccine, you could get vaccinated with a jet injector. Whatever you want, find a flu vaccine provider and see if they have your preferred vaccine.

Myth #4: People die from the flu shot. ( Fact: There have been no confirmed deaths from the flu shot .)

In late November of last year, news outlets reported a young Utah man’s death that his mother attributed to the flu vaccine. It is possible –very, very, very, very rare but technically possible – to die from the flu vaccine if you have a severe allergy to gelatin, but such anaphylactic reactions to the gelatin in a vaccine only occur to about 1 in every 2 million people, and they don’t typically die. It’s pretty unlikely that this man’s tragic death was caused by the flu vaccine, as explained here. It’s not impossible, but there is no evidence for the assertion, and no confirmed death due to the flu vaccine has ever been recorded. Certainly, people have died after getting a flu shot, just as people have gotten into car accidents right after buying ice cream sundaes. But simply dying after getting the flu shot doesn’t mean the death was caused by the flu shot, as a friend once said, any more than dying after swigging a pumpkin spice latte means the pumpkin spice latte killed you.

Myth #5: Deaths from the flu are exaggerated. ( Fact: Thousands die from flu in a typical year .)

While some have claimed that flu deaths are exaggerated each year, they’re taking advantage of the fact that it’s incredibly difficult to accurately track how many people die because of the flu. First, states aren’t required to report influenza deaths. Second, not everyone who dies due to a respiratory illness is tested for the flu, and not everyone who is gets an accurate result. Third, and most importantly, people tend to die from complications of the flu, not the flu itself. (Or, as one friend put it, no one dies from falling off a building. They die from deceleration when they hit the ground.) People can also die from a pre-existing condition, such as heart disease, because their body is weakened from fighting flu.

In the U.S., an estimated 53,826 deaths occurred from flu and pneumonia combined in 2010 and 53,667 died in 2011, making combined influenza and pneumonia the eighth leading cause of death that year. But only about 8.5% of pneumonia deaths are flu-related, so those numbers cannot tell us precisely how many died only from just the flu and its complications. Flu deaths actually vary wildly from one year to the next, depending on the dominant strains (H3N2 is linked to the most deaths). A 2010 study by the CDC found they’ve ranged from a low of 3,349 deaths in 1986-87 to a high of 48,614 deaths in 2003-04. The average is probably about 23,600 deaths a year.

Myth #6: The flu vaccine gives you the flu or makes you sick. ( Fact: The flu shot can’t give you the flu .)

This is by far the most common myth I hear – even though it’s biologically not possible to catch an illness from the inactivated vaccine. Do some people become sick right after getting a flu shot? Of course – they probably caught that bug before getting the shot, and it took a few days for symptoms to appear, or they could have coincidentally caught it after the shot. Just as likely, they could have caught the bug *at* the doctor’s office or pharmacy while waiting to get the vaccine. But they didn’t get the flu from the vaccine. The flu shot takes two weeks to confer protection, and it takes 2-5 days to incubate a flu virus. A person who does come down with the flu within a week of getting the shot was already infected when they got the vaccine.

Even with the live vaccine in the nasal spray, the weakened virus cannot cause the flu in you. However, it is theoretically possible to “shed” the virus after receiving the live vaccine, thereby infecting others, though no serious cases have been reported of this occurring. When I got my nasal vaccine, the pharmacist explained that if I sneezed directly on my 6-month-old in the hour after getting the shot, it was technically possible – though highly unlikely – for my son to get ill.

Aside from an actual illness caused by a virus or bacteria, it is certainly possible for people to just feel “under the weather” or “unwell” from the side effects of the flu shot. As the immune system ramps up to produce antibodies against those influenza strains, you might experience a headache, nausea, a low fever, etc. You might feel “sick,” but you have no fallen ill from a pathogen in the flu shot, nor did you catch the flu from the shot.

Myth #7: The flu shot contains dangerous ingredients, such as mercury, formaldehyde and antifreeze. ( Fact: Flu shot ingredients are safe .)

Single dose-shots of the flu vaccine and the flu vaccine nasal sprays do not contain any mercury compounds. The multi-dose flu shot does contain a preservative called thimerosal, which breaks down into 49% ethylmercury and used to prevent bacterial contamination of the vaccine container. Ethylmercury, as I’ve discussed before, is processed differently by the body than methylmercury, the neurotoxin that can build up in the body and is found in fish. (Keep in mind the difference a letter can make in chemistry: methanol is anti-freeze while ethanol is a Chardonnay.) Ethylmercury is made of larger molecules that cannot enter the brain and exits the body within a week.

There is no danger in receiving a vaccine with thimerosal – they’re given all over the world and it’s been extensively studied, even for cumulative effects on children over several years. If you want to avoid it anyway, or if you’re allergic to thimerosal, you can simply request a flu shot without the preservative.

Formaldehyde is used in safely small amounts in several flu vaccines (Fluarix, FluLaval, Agriflu and Fluzone) to inactivate the virus so it cannot cause disease. It is not in other influenza vaccines (Afluria, FluMist and Fluvirin). Formaldehyde, as I’ve written before, also occurs naturally in fruits and vegetables: about 2,000 mcg of formaldehyde in an average banana and anywhere from 8600 to 13200 mcg in a pear. Yet the amount of formaldehyde in flu vaccines ranges from 5 µg per dose (Fluarix) to 25 µg per dose (FluLaval) to 100 µg per dose (Fluzone). For those concerned that the formaldehyde in flu shots is injected rather than consumed, consider that the human body produces formaldehyde for a variety of functions, such as making amino acids, and has about 2,600 mcg of formaldehyde per liter of blood. So the tiny amount from the flu shot – which does not stick around and accumulate – will make little difference to your body.

The claim of antifreeze being in vaccines appears to come from the use of octylphenol ethoxylate (Triton X-100) (in Fluzone) or octoxynol-10 (Triton X-100) (in Fluarix) since this name looks similar to polyethylene glycol. Polyethylene glycol is one component of antifreeze but not antifreeze itself, just as water is a component of antifreeze. But polyethylene glycol isn’t Triton X-100 anyway. Triton X-100 is a splitting agent used to break up the virus components, and it’s been shown to be safe.

Some people may have allergies to flu vaccine ingredients, such as gelatin, thimerosal or antibiotics. See Myth #22 for more on this. Find out more about specific components of flu vaccines here or, for Fluzone in particular, see my “What’s Inside” piece in the October issue of Wired Magazine. Remember, however, that ONE LETTER can make a huge difference in what you’re talking about.

Myth #8A: Pregnant women should not get the flu shot. ( Fact: Pregnant women should get the flu shot .)

Actually, the flu shot is one of the most important things a pregnant woman can get as part of her prenatal care. I got mine while pregnant last year, and the CDC recommends that all pregnant women without medical contraindications get one. The flu shot is safe for pregnant mothers, and even after their child is born, mothers who got the flu shot while pregnant have provided their babies with a bit of extra protection against acute respiratory infections. They also may reduce children’s risk of other conditions, such as bipolar disorder, associated with prenatal influenza exposure. And, moms who get the flu shot also offer their babies some protection against the flu from birth, even if they plan to breastfeed.

Myth #8B: The flu shot can cause miscarriages. ( Fact: The flu shot reduces miscarriage risk .)

Not only does the flu shot not cause miscarriage, this non-pharma-funded study in the New England Journal of Medicine actually shows that the flu shot *decreases* the risk of a miscarriages/stillbirths in pregnant women, not least because having influenza itself during pregnancy is linked to miscarriages. Interestingly, the flu shot can even reduce women’s risk of other birth complications, such as a preterm birth or an underweight baby.

Myth #8C: Pregnant women should *only* get the preservative-free flu shot. ( Fact: Pregnant women can get any inactivated flu vaccine .)

The inactivated flu vaccine, with or without the preservative thimerosal, is safe for pregnant women, exits the body quickly and will not cause developmental problems, neuropsychological conditions or any other problems in the fetus, short-term or long-term. The shot I got last year had thimerosal, and my 6-month-old is continuing to develop normally. I discussed thimerosal in greater detail above at Myth #2. (Bonus side note: Even though ethylmercury and methylmercury are quite different, it’s worth noting that even a pregnancy diet high in fish, which may expose a woman to more methylmercury, has not been found to have an effect on children’s development.)

For much more information (and research) about getting the flu shot while pregnant, check out my post specifically focused on flu vaccines during pregnancy.

Myth #9: Flu vaccines can cause Alzheimer’s disease. ( Fact: There is no link between Alzheimer’s disease and the flu vaccine; flu vaccines protect older adults.)

This myth is even addressed on the Alzheimer’s Association website, where they note the 2001 study showing a *reduced* risk of Alzheimer’s among those who had received flu vaccines, the polio vaccine and the tetanus and diphtheria vaccines. In fact, the risk for developing Alzheimer’s was half as much for those receiving these vaccines. This myth originated with a quack named Hugh Fudenberg who has no evidence for the claim.

Meanwhile, seniors are at high risk for flu complications and death and are recommended to get the flu vaccine each year, specifically the high-dose flu vaccine, since it offers greater protection for adults aged 65 and older, according to new research. The live vaccine and the intradermal flu vaccine are not recommended for those over 65. (Side note: some worry about aluminum in vaccines causing Alzheimer’s — except that flu shots don’t contain aluminum and aluminum does not cause Alzheimer’s.)

Myth #10: Pharmaceutical companies make a massive profit off flu vaccines. ( Fact: They’re a tiny source of pharma profit .)

There is no question that pharmaceutical companies are for-profit companies taking in billions and billions of dollars. Making money, however, does not mean one is immoral by default. Car seat manufacturers turn a profit, but that doesn’t mean we refuse to buy car seats on principle. That said, there have been plenty enough shady dealings, lawsuits, investigations and other such incidents to support a healthy suspicion of Big Pharma and its motives. But vaccines simply don’t offer enough revenue to a difference here.

If pharmaceutical companies didn’t make a profit off vaccines, they wouldn’t manufacture them. At the same time, vaccine profits are a drop in the bucket compared to profits from medications for chronic conditions such as high blood pressure and mental illnesses, not to mention the cash flow from drugs like Viagra. In fact, the top three flu vaccine manufacturers – Sanofi Pasteur, Glaxo SmithKline and Novartis – pulled in about $3.1 billion from flu vaccines in 2013. Yep, that’s billions. But total pharmaceutical companies revenues last year were nearly $1 trillion – making the bulk of flu vaccine revenue only about 0.3% of total revenue. For those big three companies, flu vaccines comprise about 4.5% of total annual revenue. (Meanwhile, cholesterol-lowering drugs such as statins raked in $35 billion back in 2011.) For an even more in-depth look at these numbers, check out Skeptical Raptor’s post on Big Pharma profits from flu vaccines. He’s run the numbers and made it clear that flu vaccines just aren’t profitable enough to justify some grand conspiracy.

Meanwhile, the recommendations for vaccines come from public health organizations such as the CDC and similar public health, government and academic institutions across the world. Unless you think all those countries’ governments and public health officials are involved in a huge conspiracy or money-making scheme with Big Pharma (and if you think that, read this), then the fact that vaccines offer a profit to pharma companies isn’t a reason not to get vaccinated. In fact, influenza itself is quite costly, costing the US about $4.6 billion annually in direct medical costs and as much as $87 billion annually in all costs.

Myth #11: Flu vaccines don’t work. ( Fact: Flu vaccines reduce the risk of flu. )

Flu vaccines are not 100% effective. (Actually, no vaccine is 100% effective.) But they do reduce the risk of catching the flu even if they cannot eliminate the risk. And there are tons of studies showing this (and yes, many of these are not funded by Pharma). Unfortunately, the effectiveness of the flu vaccine varies quite a bit from year to year, and it’s among the less effective vaccines compared to ones such as the measles-mumps-rubella vaccine, whose effectiveness for measles is in the high upper 90%s. (The more people who get the vaccine, though, the better herd immunity is and the more effective it can be.)

There are a couple things to keep in mind about the effectiveness of the flu vaccine that vaccine researcher Jessica Atwell explained. First, the flu vaccine has historically protected against only three strains each year (though the four-strain vaccines are becoming more popular), but there are many more strains circulating each year. The World Health Organization make educated guesses by February about which strains will be circulating later that fall: some years their algorithms for picking the strains are better than others. Last year, they did pretty well. Of more than 5,600 influenza viruses characterized during the 2013-2014 season, 99.8% of the H1N1 viruses were the strain in the vaccine that year, 95.3% of the H3N2 viruses were the vaccine strain, and 70.3% of the influenza B viruses were the vaccine strain. Another 29.4% of the influenza B viruses were the strain included in last year’s quadrivalent vaccine.

Yet even in the years when their estimates fall short, the flu shot is worthwhile: a meta-analysis looking at 34 randomized, controlled trials across 47 flu seasons found that even when the strains in the flu vaccine do not match the strains circulating that year, the flu vaccine offered a measure of protection against the circulating strains.

Next, the effectiveness of the flu vaccine varies for different age groups, partly because of the way the immune system ages. “Generally speaking, your immune system peaks in early adulthood and goes downhill from there – hence less than ideal efficacy of standard flu vaccines in the elderly,” Atwell said. (Though, again, the high-dose flu vaccine shows better effectiveness in the elderly in an August 2014 study in NEJM.) Yet even studies showing low overall effectiveness — this one found anywhere from 33 to 100 adults need to be vaccinated each year to prevent one case of the flu — still show a reduced risk of the flu in vaccinated individuals. Coming at it from a different angle, another recent study estimated that vaccination prevented anywhere from 1.1 million to 5 million flu infections during each flu season over six years.

Again, some years, the flu vaccine’s effectiveness is very low. Other years, it’s better. But just because it does not work 100% all the time for all people does not mean it’s worthless or ineffective. Some days, I feel like I’m only operating at 50% human capacity — but I still need to be a mother to my son, and I’m better than no parent at all for him. Or, for a simpler analogy: If there is a 50% chance it’s going to rain, do you take along the umbrella even if it’s an inconvenience? Some do because they don’t want to get wet if it does rain. Some bring it, but it’s a bad storm and they get a little wet anyway. Others don’t bring the umbrella. The difference? If you don’t bring an umbrella, it’s just you getting wet, but by not getting yourself vaccinated, you potentially put others at risk for catching the flu from you, if you catch it.

The Holy Grail, of course, is a universal flu vaccine to provide protection against many or all influenza strains. It’s a goal that many flu vaccine researchers have been working toward for years, but there are many challenges to such a vaccine and success has been elusive.

Myth #12: Flu vaccines don’t work for children. (Fact: Flu vaccines reduce children’s risk of flu. )

As noted above, the effectiveness of the flu vaccine varies by age and by which vaccine (live or inactivated) a person gets, but there is no doubt that it offers some protection against the flu. As Melinda Wenner Moyer points out in this Slate piece, the live vaccine (FluMist) is more effective for kids aged 2 to 7, up to 83% effective (meaning kids who get the vaccine are 83% less likely to get the flu than gets who aren’t vaccinated). To put that study’s finding in absolute number terms, 16% of unvaxed kids got the flu compared to 3.4% of those who received the live vaccine. In fact, the higher effectiveness of the nasal vaccine – found again in a study this past January – is what led to the recommendation this year that children aged 2 to 8 get the FluMist if possible and not contraindicated because it’s about 50% more effective for kids in this age group than the flu shot is. (A recent study found that even children with cystic fibrosis did well with the live vaccine.)

In fact, the (inactivated) shot only offered 48% effectiveness in another study. (Moyer’s article is worth reading in full for more details about flu vaccine effectiveness in children and teens.) Another review of the research found that, for children under 6 years old, one child would be prevented from contracting influenza for every six who were vaccinated with the live vaccine. For children over 6, one case of flu could be prevented for every 28 kids who received the inactivated vaccine.

Moyer also notes that the research on the effectiveness of the flu for kids aged 6 months to 2 years is weak, mostly because there isn’t much data available. (That’s based on a Cochrane review whose only data set on children under 2 was a study with 16 infants.) It’s true the data is thin, but it’s not entirely nonexistent, and new research, such as the NEJM study on the nasal vaccine and this one in The Lancet, has come out showing flu vaccine effectiveness in kids since the Cochrane Review. The CDC notes that one study found the flu vaccine to be 66% effective in preventing lab-confirmed influenza in children aged 6 months to 2 years old. (While this study did not find the flu vaccine to help prevent ear infections, others have found that.) Another study has found a good immune response to the vaccine among children (including infants). In another, focused specifically on children aged 9 months to 3 years, only 4% of vaccinated children under age 2 caught the flu compared to 12% of the unvaccinated children, for another finding of 66% effectiveness.

Myth #13: Flu vaccines make it easier for people to catch pneumonia or other infectious diseases. ( Fact: Flu vaccines reduce the risk of pneumonia and other illnesses. )

This myth is just bizarre. For one thing, catching the flu will weaken your immune system while you’re sick, during which it’s easier to become ill from other bugs. But more importantly, pneumonia is among the most common complications to occur as a result of a flu infection, so getting the flu shot *reduces* your risk of pneumonia, a leading cause of death among those who die from influenza complications.

Myth #14: Flu vaccines cause vascular or cardiovascular disorders. ( Fact: Flu shots reduce the risk of heart attacks and stroke. )

This is another myth that should be flipped on its head. There is no evidence that the flu vaccine causes vascular disorders. Meanwhile, the vaccine has been shown in multiple studies to reduce individuals’ risk of heart attacks, stroke and other cardiovascular events.

Myth #15: Flu vaccines can break the “blood brain barrier” of young children, hindering their development. ( Fact: Flu vaccines have been found safe for children 6 months and older. )

There is no evidence that flu vaccines can hurt children’s development or that children’s neurovascular structure are affected by flu vaccines. A child’s blood brain barrier is formed in utero and is functional from birth in regulating what can and cannot pass into the brain. Researchers at Stanford University and the University of California – San Francisco discovered in 2010 that pericytes are required for blood-brain barrier development and that pericytes are present in the fetal brain. This research shows that an infant’s blood brain barrier is developed before birth. The physiology of the blood brain barrier and how it functions at that level of development make it highly implausible that any vaccine components could penetrate the barrier.

Myth #16: Flu vaccines cause narcolepsy. ( Fact: The U.S. seasonal flu vaccine does not cause narcolepsy. )

This is one of the few misconceptions that is rooted in a small amount of fact, though it’s often misrepresented or blown out of proportion. Narcolepsy is a neurological disorder in which the brain in unable to regulate sleep-wake cycles. Several studies, first in Finland and then in other European countries, found and confirmed a link between narcolepsy and the 2009 H1N1 flu vaccine called Pandemrix, manufactured by GlaxoSmithKline Europe and used in several European countries (but not in the U.S. or Canada). It was not used before 2009 or since the 2009-2010 season, and no links to narcolepsy have been found for U.S.-manufactured H1N1 or seasonal flu vaccines. The CDC is sponsoring an international study on the link between the 2009 H1N1 flu vaccines and narcolepsy, expected to be completed in 2014.

One hypothesis for the link relates to an adjuvant called ASO3, an oil-in-water emulsion. Adjuvants are substances added to a vaccine to increase the body’s immune response to that vaccine; U.S. influenza vaccines do not contain adjuvants. Other possibilities for the narcolepsy risk include immune stimulation from the vaccine itself, immune activation from H1N1 infection or another infection present at the time, or a combination of these factors. It’s also possible the narcolepsy risk is related to the H1N1 virus itself, which could means the flu infection could increase the risk of narcolepsy — but these are all conjectures at the moment. Recommendations in Europe were initially revised for the vaccine and then Pandemrix was suspended after the evidence came to light. The increased risk was estimated at an additional 3 to 7 cases of narcolepsy for every 100,000 vaccinated children (the link was only seen in those under 21).

Myth #17: The flu vaccine weakens your body’s immune response. ( Fact: The flu vaccine prepares your immune system to fight influenza. )

Vaccines do not weaken the body’s immunological responses or cause other infections. They actually strengthen the immune system, activating a response that leads to the production of specific antibodies against the disease the vaccine is designed to protect against. The immune system is like a muscle and vaccines are like the exercise. The vaccines train your immune system for a future attack just like exercise strengthens your muscles and makes you body stronger. (The flu, on the other hand, does weaken your immune system while your body tries to fight it.)

Myth #18: The flu vaccine causes nerve disorders such as Guillain-Barré syndrome. ( Fact: Influenza is more likely than the flu shot to cause Guillain-Barré syndrome. )

Guillain Barre syndrome (GBS) is an autoimmune disorder in which the immune system mistakenly attacks a person’s own nerve tissue, causing muscle weakness and sometimes temporary paralysis. The disorder affects approximately one person out of every 100,000 individuals. Causes are not well understood, though the disorder has been linked to viruses including cytomegalovirus, Epstein Barr and influenza (as well as the bacteria campylobacter).

This misconception, like the one about narcolepsy, is partly based on fact because the 1976 H1N1 flu vaccine was found to be linked to a higher risk of GBS that year – approximately 10 additional cases of GBS for every 1 million people vaccinated. Since then, GBS risk has probably been the single most studied adverse event from the flu shot in the history of flu shot research, and the majority of it has shown no increased risk with seasonal flu vaccinations. One study that investigated the risk of GBS from the flu shot among more than 30,000 million “person-years” (30 million people over an 11-year period) found no increased risk for the flu shot. Based on numerous studies, the independent Institute of Medicine “concluded that there was sufficient evidence to reject an association between influenza vaccination and GBS.”

Another study specifically on the 2009-2010 H1N1 vaccine did find an increased risk of GBS — but not as high as the risk of GBS from the flu itself (or the risk of death from the flu). It found a risk of 1 additional case of GBS per every 1 million vaccinations and 17 additional cases of GBS for every 1 million influenza infections. That flu season, the H1N1 influenza killed about 280,000 worldwide (more than 12,000 of whom were in the U.S., which recorded 61 million H1N1 infections during 2009). Finally, one study did find a slightly higher risk – 1.6 cases of GBS per 1 million vaccinations – for seasonal flu vaccines and the H1N1, but this increased risk in seasonal vaccines has not been found in other studies.

Myth #19: The flu vaccine can make you walk backwards or cause other neurological disorders. ( Fact: Neurological side effects linked to flu vaccination are extremely rare (see Myth #18), but influenza can cause neurological complications. )

Remember that bizarre case of the cheerleader who said she got a flu shot and then she could only walk normally backwards, not forwards? She claimed she had developed a neurological disorder called dystonia that was triggered by the flu shot. There was a pretty significant problems with her story, however: all the experts looking at videos of the young woman said her symptoms appeared “psychogenic,” which means they were psychological, not neurological, in origin. That doesn’t make them less real, but it means the flu shot didn’t cause them. In fact, epidemiologist Rene Najera looked up the girl’s case report in the Vaccine Adverse Event Reporting System (VAERS) and found this: “The admitting neurologist felt that there was a strong psychogenic component to the symptomology, and made a final diagnosis of weakness.” So even the physician who directly examined her concluded her symptoms were most likely psychological.

Excluding Guillain-Barré syndrome, which Myth #18 addresses above, there is no evidence that the flu vaccine can cause neurological disorders, but there is evidence that influenza can. In fact, children with neurological disorders or other neurodevelopmental conditions are especially encouraged to get the vaccine because they are at a higher risk of complications from influenza than other children. Almost half of the children who died from the flu during the 2009 season had underlying neurological disorders, such as epilepsy or cognitive dysfunction.

Myth #20: Influenza isn’t that bad. Or, people recover quickly from it. ( Fact: Influenza knocks most people down *hard*. )

Influenza is a serious illness. The symptoms are similar to other illnesses, so people often mistake milder illnesses for the flu. Some lucky folks do recover in a day or two, but most are down for a week or two, and complications can be life-threatening, especially complications in children. A recent study found that half the children hospitalized in Australia during the 2009 pandemic had previously been healthy with no underlying conditions. Not everyone gets a fever, but having the flu isn’t pleasant, especially given the minor side effects or low risks for serious side effects from the vaccine.

During last year’s 2013-2014 season, more than 9,600 hospitalizations were reported as a result of laboratory-confirmed flu during the 2013-2014 season – but those are just lab-confirmed flu (many cases of the flu are never lab tested), and the reported cases represent only about 8.5% of the U.S. population. If we assume – in a very rough estimate – that flu hospitalizations are evenly distributed throughout the U.S., that means there were likely more than 113,000 hospitalizations from just laboratory-confirmed flu during the 2013-2014 season. Among adults aged 65 and older, 88 out of every 100,000 hospitalizations were flu-related. The next highest rates were for adults aged 50 to 64, who were hospitalized at a rate of 54 per 100,000 admissions, and children younger than 5 years old: 47 of every 100,000 hospitalization was flu-related. But even healthy young adults ended up in the hospital with flu: Almost two-thirds of the hospitalizations (60%) were adults between 18 and 64 years old.

Myth #21: People don’t die from the flu unless they have another underlying condition already. (Fact: Otherwise healthy people DO die from the flu.)

People die from the flu. Every year. This includes adults who are healthy up until getting the flu and it includes children with no underlying conditions (plenty of unfortunate stories here). In 2013, in fact, 90% of the children who died from the flu had not been vaccinated. The annual numbers of lab-confirmed flu deaths in children are not high, but they are potentially preventable. A study published in Pediatrics last year reported that 43% of the more than 800 children who died from the flu between 2004 and 2012 had no underlying medical conditions. Often, influenza might contribute to a death but not be listed on the death certificate if the individual died from complications of the flu, such as pneumonia. And last year in particular, the H1N1 strains of the flu hit healthy adults – the “young invincibles” – particularly hard. So yes, the flu can kill you. Even if you take vitamins, eat healthfully, exercise daily, drink water and practice good hygiene.

Myth #22: People with egg allergies cannot get the flu shot. ( Fact: People with egg allergies can get a flu shot .)

First of all, as explained in Myth #3, there are a variety of flu vaccine options, including two that are manufactured without using eggs. The recombinant vaccine Flublok, first made available last year for those aged 18 to 49, and the cell-culture-based vaccine Flucelvax, approved in 2012, are both egg-free. For those not in that age ranges, or if one of these vaccines is unavailable in your area, the American College of Allergy, Asthma & Immunology states clearly, “People with egg allergy are not at any additional risk of having a reaction when given the flu vaccine even though the vaccine may contain some amount of egg protein.” This statement is based on the evidence in their influenza vaccination recommendations (paywall), summarized here. This also refers to non-severe egg allergies, and the CDC has provided a helpful flowchart for those with egg allergies planning to get the flu vaccine.

There are some allergic reactions that can occur with the flu shot. Some people are allergic to thimerosal and should get the preservative-free shot. Some people are allergic to antibiotics and should get flu vaccines without added antibiotics. (The antibiotic polymyxin is in Afluria and Flurvirin, for example, and Fluvirin also contains neomycin.) And in very rare cases – about 1 in every 1-2 million doses of all vaccines – individuals with severe allergies to gelatin can have an anaphylactic reaction. If you have an egg allergy that causes an anaphylactic reaction, ask your allergist to administer the shot.

Myth #23: If I get the flu, antibiotics will take care of me. ( Fact: Antibiotics can’t treat a viral infection. )

Influenza is a virus. Antibiotics fight bacteria (anti = “against”; biotics = “of life,” referring to living bacteria). All the antibiotics in the world won’t help you fight off a flu infection. (P.S. Neither will essential oils; there is no evidence to support any essential oils curing the flu.)

Myth #24: The flu shot doesn’t work for me, personally, because last time I got it, I got the flu anyway. ( Fact: The flu shot cannot guarantee you won’t get the flu, but it reduces your risk. )

As noted further up, getting the flu vaccine does not guarantee you won’t catch the flu. It does reduce your risk of getting the flu, and it can lead you to have a milder course of the illness than if you hadn’t been vaccinated. It’s also entirely possible that you catch a strain of the flu not covered in the vaccine.

Myth #25: I never get the flu, so I don’t need the shot. (Fact: You can’t predict whether you’ll get the flu.)

Millions of people have never gotten into car accidents. They still wear seat belts and carry car insurance. I’ve never been struck by lightning. But if there’s a thunderstorm raging, I avoid standing outside in wide open fields. It’s estimated that 6%-7% of adults (pdf) and about 20% of children under 5 get the flu each year. The past is no indicator of whether you’ll end up in that percentage this year any more than flipping a coin to heads tells me what the next flip will be.

Myth #26: I can protect myself from the flu by eating right and washing my hands regularly. ( Fact: A good diet and good hygiene alone cannot prevent the flu. )

Influenza is an airborne virus, so although hand-washing is important and can reduce your risk of becoming ill from germs in general, all the hand-washing in the world won’t guarantee you don’t catch the flu. Eating a healthy, balanced diet is also important, and certainly being healthy makes it easier for your immune system to fight off new infections. But simply eating well cannot magically prevent you from being exposed to the flu virus.

Myth #27: It’s okay if I get the flu because it will make my immune system stronger. ( Fact: The flu weakens your immune system while you’re body is fighting it and puts others at risk. )

As noted above, your immune system is weakened while you’re ill from the flu. While your immune system may be strengthened after you recover against that particular strain or a (theoretical) future related strain, a vaccine primes your immune system to fight off influenza strains in the same way (without the week of fever, chills and vomiting). Additionally, if you catch the flu, you are contagious to others. Being vaccinated helps keep herd immunity levels higher in your community, especially protecting those who are weaker or cannot be vaccinated.

Myth #28: If I do get the flu, I’ll just stay home so I’m not infecting others. ( Fact: You can transmit the flu without showing symptoms. )

I’m glad you’ll stay home, but there are two problems with this plan. First, you’re contagious before symptoms appear, so you could infect someone before you even know you’re sick. Second, you could catch the flu but remain asymptomatic – showing no symptoms. That’s lucky for you but not for those around you whom you could infect. It’s unlikely, but you’re still putting others at risk.

Myth #29: Making a new vaccine each year only makes influenza strains stronger. ( Fact: There’s no evidence flu vaccines have a major effect on virus mutations. )

This myth is a challenging one to address succinctly without oversimplifying the science. The short answer is that current vaccines are not going to create more dangerous variants of a flu strain.

Influenza virus strains are evolving and changing on a regular basis in two main ways: “antigenic drift and antigenic shift.” Drifts are small, gradual changes that happen all the time in response to environmental pressure and even within our own bodies. The influenza virus has a segmented genome: its genome is in eight parts which can randomly re-assort. When the virus infects an individual, it can “exchange” these gene segments and change within that one individual. Our own immune response can invoke a selective pressure on the virus that contributes to drifting, with or without a vaccine. If the virus didn’t change at all from year to year, the flu vaccine would never need to be reformulated each year (and that Holy Grail of a universal flu vaccine would be less elusive).

It is possible that a vaccine could be among the environmental pressures influencing antigenic drifts, but no more so than what already occurs in our own bodies and most likely to a lesser extent. There is not evidence that vaccines cause major changes in the virus, such as an antigenic shift. A shift is much more troublesome change, leading to a dramatically different strain that our immune systems are not usually prepared for. A shift is what happened with the 2009 H1N1, and it’s what happened with the Spanish flu epidemic in 1918-1919. That pandemic only lasted a year, but it was far worse than a typical flu season, killing an estimated 3% of the world population. (More on this in this book.)

Interestingly, some believe it’s possible that high levels of herd immunity could reduce antigenic drift. This researcher explains, “As herd immunity increases, we should expect to see more antigenic drift; however, if immunity is high enough to prevent the population-wide spread of the pathogen, the epidemic cannot take off and the virus does not evolve.” Regardless, current vaccines are not going to create more dangerous variants of a flu strain.

Myth #30: The side effects of the flu shot are worse than the flu. ( Fact: The flu is worse than flu shot side effects. )

The most common side effects of the flu vaccine are aches, itching, fatigue, headache, fever, hoarseness, sore or red and itchy eyes, a cough and soreness, redness or swelling where the shot was given and aches. Young children may, in rare cases, develop a high fever (a febrile seizure) that can result in a short seizure, not causing long-term damage. (Febrile seizures are not uncommon in young children generally.) The most serious risk is an allergic reaction, possible in approximately 1 out of every 1 to 2 million doses. In the H1N1 vaccines already noted above, Guillan Barre syndrome may be an increased risk for 1 to 2 of every 1 million doses, though it’s many times more common from influenza itself.

The flu itself, as noted above, is much more serious and can cause death.

Myth #31: The “stomach flu” is the flu. ( Fact: The “stomach flu” is a generic term for gastrointestinal illnesses unrelated to influenza. )

Ever heard someone talk about a bad case of the “stomach flu?” People refer to any number of gastrointestinal illnesses that way, but the “stomach flu” isn’t related to the actual influenza virus. It’s just sloppy use of language. Most people talking about the stomach flu have diarrhea and vomiting, but without the fever and aches, that’s unlikely to be the real-deal flu.

Myth #32: If you haven’t gotten a flu shot by November, there’s no point in getting one. ( Fact: Getting a flu shot at any time during flu season will reduce your risk of getting the flu. )

Flu season continues well into January and February, not really petering out until late March or April, and flu vaccines tend to be available throughout that time. It only takes two weeks for your immune system to make the antibodies that offer protection, so it’s basically never too late to get the flu shot until flu season is over.

Myth #33: The flu vaccine causes Bell’s palsy. (Fact: The flu shot does not cause Bell’s palsy.)

One of the many conditions once thought potentially linked to the flu vaccine is Bell’s palsy, a condition of uncertain origins, though it’s been linked to a range of viral infections. It appears that one flu vaccine used in Switzerland during the 2000-2001 season might have been linked to an increased risk of Bell’s palsy (46 cases). An investigation of U.S. reports in the decade prior also appeared to show a risk, which led to a more in-depth study. That in-depth one found no increased risk, which a report from the independent Institute of Medicine found as well. In addition, a study looking specifically for Bell’s palsy risks in children after a flu vaccination found no increased risk. Sometimes it can be tough to separate cause from correlation and to determine whether two things that happen at the same time are related or coincidence — hence the reason for multiple studies.

However, it is important that adverse events occurring after any vaccine is given are reported to the Vaccine Adverse Event Reporting System (VAERS) so that researchers can follow up on conditions that are reported multiple times. It’s best that a doctor make the report since medically confirmed events are generally given better weight. This is how new associations, such as the narcolepsy link with the European 2009 H1N1 Pandemrix vaccine, are identified.

Please ask questions, provide new information, etc. in the comments. However, any comments which include inaccurate information posing as “warnings” or “countering” accurate info will be deleted. I encourage debate but not the dispersal of misinformation.

If you’ve read the alarmist “Should I Get the Flu Shot?” post from “Food Babe,” here’s a great, in-depth debunking of that piece.

Special thanks to the extensive research for this post goes to Kathy McGrath, Nathan Boonstra, Jessica Atwell, Rene Najera, Amber Bickford Cox, Karen Ernst and Emily Willingham.