written by Tara Haelle

CAUTION: This post is more than three years old and likely contains broken links or outdated information. A new link to this year’s article will be added here when available.

It’s that time again — that time when dozens of spurious articles pop up all over the web touting all the dangers of the flu vaccine. Articles on unreliable, alarmist, misinformative sites like Natural News, Mercola, chiropractic blogs and other such sites rail against the “toxins” in the vaccine, or claim the flu vaccine doesn’t work, or that it causes this or that horrible disease, or that the flu itself just really isn’t all that bad. (I’m not going to link to any of them. They get too much attention as it is.)

I could be wrong, but I’d venture to guess there is more nonsense and misinformation about the flu vaccine than any other vaccine out there. Perhaps it’s because it’s a once-a-year vaccine, so that cyclical nature brings out new myths each year. Or maybe it’s because it’s for an illness that many people have had, even more than once, and survived, so they mistakenly assume a vaccine is unnecessary.

Whatever the reasons, I’ve decided a comprehensive post addressing every myth I’ve been able to find is long overdue. I plan to update this post as necessary, and I’ll likely republish it each year as a reference. Note all the links where I provide my sources — more than half of these go directly to peer-reviewed medical research.

To make it easier to navigate, I’ve listed all 25 myths here at the top with links to that myth’s debunking explanation.

First, an important note: I am a science journalist but not a medical doctor. 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 2013-2014 flu vaccines (including information on which vaccines pregnant women, the elderly and children under 2 should *not* get), please consult the CDC site directly.

Myth #1: The flu vaccine gives you the flu or makes you sick. (No, it doesn’t.)

Myth #2: Flu vaccines contains dangerous ingredients, such as mercury, formaldehyde and antifreeze. (Not exactly, and the ingredients aren’t dangerous.)

Myth #3: Pregnant women should not get the flu shot. (They should.) / The flu shot can cause miscarriages. (It doesn’t.) / Pregnant should only get the preservative-free flu shot. (Nope.)

Myth #4: Flu vaccines can cause Alzheimer’s disease. (They can’t.)

Myth #5: Flu vaccines provide billions of dollars in profits for pharmaceutical companies. (Maybe, maybe not, but so what?)

Myth #6: Flu vaccines don’t work. (Um, they do work.)

Myth #7: Flu vaccines don’t work for children. (Again, they work.)

Myth #8: Flu vaccines make it easier for people to catch pneumonia or other infectious diseases. (No, they make it harder.)

Myth #9: Flu vaccines cause vascular or cardiovascular disorders. (No, they don’t.)

Myth #10: Flu vaccines can break the “blood brain barrier” of young children and hurt their development. (No, they can’t.)

Myth #11: Flu vaccines cause narcolepsy. (Not the seasonal flu vaccine, and not most others.)

Myth #12: The flu vaccine weakens your body’s immune response. (It actually strengthens it.)

Myth #13: The flu vaccine causes nerve disorders such as Guillain Barre syndrome. (Extremely rarely – and more commonly with flu infections.)

Myth #14: The flu vaccine can cause neurological disorders. (No, it can’t.)

Myth #15: Influenza isn’t that bad. Or, people recover quickly from it. (Uh, it’s pretty bad.)

Myth #16: People don’t die from the flu unless they have another underlying condition already. (Actually, healthy people DO die from the flu.)

Myth #17: People with egg allergies cannot get the flu shot. It will kill them! (No, it won’t, and there’s an egg-free vaccine.)

Myth #18: If I get the flu, antibiotics will take care of me. (No, they can’t.)

Myth #19: The flu shot doesn’t work for me, personally, because last time I got it, I got the flu anyway. (It still reduces your risk.)

Myth #20: I never get the flu, so I don’t need the shot. (You can see the future?)

Myth #21: I can protect myself from the flu by eating right and washing my hands regularly. (No, you can’t.)

Myth #22: It’s okay if I get the flu because it will make my immune system stronger. (Selfish, much? And no, it doesn’t.)

Myth #23: Making a new vaccine each year only makes influenza strains stronger. (No, it doesn’t.)

Myth #24: The side effects of the flu shot are worse than the flu. (No, they aren’t.)

Myth #25: The flu vaccine causes Bell’s palsy. (No, it doesn’t.)

Myth #1: The flu vaccine gives you the flu or makes you sick. (No, it doesn’t.)

This is by far the most common myth I hear – even though it’s biologically not possible from the inactivated vaccine. Are there people who become sick right after having gotten the flu shot? Of course, and it’s an illness they had likely caught before the shot and it took a a few days for symptoms to appear, or it’s just coincidence (and it may or may not be the flu). 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. 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.

Edit: One thing worth noting is that some people may feel “under the weather” or generally crappy for a few days after the shot or a week or two later. A headache, nausea, fever, etc. can be a result of the side effects of the vaccine, usually from the immune system ramping up and producing antibodies against those influenza strains. Some may consider this feeling “sick,” but you are not sick in the sense that the flu vaccine caused you to fall ill from a pathogen, and the vaccine certainly didn’t give you the flu.

Myth #2: The flu shot contains dangerous ingredients, such as mercury, formaldehyde and antifreeze. (Not exactly, and the ingredients aren’t dangerous.)



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. And, keep in mind, if you’re just one of those paranoid types, you can easily request and get 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 also occurs naturally in fruits and vegetables even is produced by the human body for a variety of functions, including making amino acids. The amounts of formaldehyde in these vaccines vary from 5 µg per dose (Fluarix) to 25 µg per dose (FluLaval) to 100 µg per dose (Fluzone). For reference, a pear contains about 39 to 60 mg/kg of formaldehyde (1000µg = 1mg, so pears contains approximately 39,000 to 60,000 µg/kg.) A typical pear weighs about 220g, or 0.22 kg. That means a single pear would contain 0.22 times the 39 to 60 mg/kg, or 8.6 to 13.2 mg (8600 to 13200 µg). (Meanwhile, a single dried shiitake mushroom contains 100-406 mg/kg of formaldehyde.)

The claim of antifreeze being in vaccines comes from the use of octylphenol ethoxylate (Triton X-100) (in Fluzone) or octoxynol-10 (Triton X-100) (in Fluarix) used to inactivate those viruses or to purify other vaccines. Polyethylene glycol by itself is one component of antifreeze but is not antifreeze itself, just as water is a component of antifreeze. But these are not the same as polyethylene glycol and involve the use of Triton X-100 as a splitting agent, which has been shown to be safe. Learn more about specific components of flu vaccines here, but remember, again that ONE LETTER can make a huge difference in what you’re talking about.

Myth #3A: Pregnant women should not get the flu shot. (They should.)



I’m pregnant, and I got the flu shot last week, as should all pregnant women without medical contraindications, as the CDC recommends. 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 #3B: The flu shot can cause miscarriages. (It doesn’t.)



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 #3C: Pregnant women should *only* get the preservative-free flu shot. (Nope.)



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 (or any other problems) in the fetus. The shot I got last week had thimerosal, and I’m certainly not going to do anything to hurt my developing baby. 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.)

Myth #4: Flu vaccines can cause Alzheimer’s disease. (They can’t.)



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. The myth originated with a quack named Hugh Fudenberg who has no evidence for the claim.

Meanwhile, seniors are at a higher risk for flu complications and death and are recommended to get the flu vaccine each year, particularly the inactivated (not live) vaccine for those over 65 years old. The intradermal flu vaccine is also 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 #5: Flu vaccines provide billions of dollars in profits for pharmaceutical companies. (Maybe, maybe not, but so what?)



There is no question that pharmaceutical companies are for-profit companies and that they really rake in the billions. If they didn’t make a profit off vaccine, they wouldn’t manufacture them. However, the profits they earn from vaccines are a drop in the bucket when considered along with chronic condition medications such as blood pressure meds and mental health drugs, not to mention the cash flow from medications like Viagra.

But the recommendations for vaccines come from public health organizations such as the Centers for Disease Control 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 #6: Flu vaccines don’t work. (Um, they do work.)



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. Unfortunately, the effectiveness of the flu vaccine varies quite a bit from year to year and is among the less effective vaccines compared to ones such as the measles-mumps-rubella vaccine, whose effectiveness 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 mentioned to me. First, the flu vaccine has historically protected against only three strains each year (the live vaccine FluMist this year protects against four for the first time this year), 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. Yet in even 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. 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? 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 #7: Flu vaccines don’t work for children. (Again, they work.)



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.

Meanwhile, 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. 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 #8: Flu vaccines make it easier for people to catch pneumonia or other infectious diseases. (No, they make it harder.)



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 #9: Flu vaccines cause vascular or cardiovascular disorders. (No, they don’t.)



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 #10: Flu vaccines can break the “blood brain barrier” of young children and hurt their development. (No, they can’t.)



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 #11: Flu vaccines cause narcolepsy. (Not the seasonal flu vaccine, and not most others.)



This is one of the few myths 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 US or Canada). It was not used before 2009 or since the 2009-2010 season, and no links to narcolepsy have been found for US-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; US 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 #12: The flu vaccine weakens your body’s immune response. (It actually strengthens it.)



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 #13: The flu vaccine causes nerve disorders such as Guillain Barre syndrome. (Extremely rarely – and more commonly with flu infections.)



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 myth, 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 US, 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 #14: The flu vaccine can cause neurological disorders. (No, it can’t.)



There is no evidence that the flu vaccine can cause neurological disorders, but there is evidence that influenza can. Meanwhile, 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 #15: Influenza isn’t that bad. Or, people recover quickly from it. (Uh, it’s pretty bad.)



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 few days, but most are down for a week or two, and complications can be life-threatening, especially complications in children. 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.

Myth #16: People don’t die from the flu unless they have another underlying condition already. (Actually, healthy people DO die from the flu.)



People die from the flu. Every year. This includes children with no underlying conditions (plenty of unfortunate stories here). In fact, a study published just today in Pediatrics 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.

Myth #17: People with egg allergies cannot get the flu shot. It will kill them! (No, it won’t, and there’s an egg-free vaccine.)



Before debunking this myth, it’s important that people know the flu vaccine Flublok, available for the first time this year, is manufactured without eggs. Recommended by the CDC earlier this year, Flublok is recommended only for those aged 18 to 49.

For those not in that age range, or if the new vaccine is unavailable, 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.

Myth #18: If I get the flu, antibiotics will take care of me. (No, they can’t.)



Influenza is a virus. Antibiotics fight bacteria (anti = “against”; biotics = “of life,” referring to living bacteria, not to viruses). All the antibiotics in the world won’t help you fight off a flu infection.

Myth #19: The flu shot doesn’t work for me, personally, because last time I got it, I got the flu anyway. (It still 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 #20: I never get the flu, so I don’t need the shot. (You can see the future?)



Millions of people have never gotten into car accidents. They still wear seat belts and carry insurance.

Myth #21: I can protect myself from the flu by eating right and washing my hands regularly. (No, you can’t.)



Influenza is an airborne virus, so although hand-washing is important and can reduce your risk of becoming ill from other germs, it does not affect your risk of catching 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 #22: It’s okay if I get the flu because it will make my immune system stronger. (Selfish much? And no, it doesn’t.)



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, 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 #23: Making a new vaccine each year only makes influenza strains stronger. (No, it doesn’t.)



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 how viruses work can be found 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 #24: The side effects of the flu shot are worse than the flu. (No, they aren’t.)



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. The most serious risk is an allergic reaction, possible in approximately 1 out of every 1 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 #25: The flu vaccine causes Bell’s palsy. (No, it doesn’t.)



As I was writing this post, a friend notified me that their spouse had developed Bell’s palsy following the flu shot. I have not heard this mentioned as a myth, so I investigated it. 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 US 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. Most likely, based on the research known to date, the friend’s spouse developed Bell’s palsy for another reason that occurred unfortunately at the same time as the flu shot (the condition can be caused by a wide range of viral infections, including the flu itself). Since the report occurred this year, there is insufficient evidence to determine for certain if it is related to the flu shot or not; it’s only possible to hypothesize that it wasn’t based on past evidence. But the friend should report it to VAERS nonetheless. 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.

For another great debunking of flu myths about the H1N1 vaccine, which also apply to some of the myths of the seasonal flu vaccine, check out Emily Willingham’s post here.

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 and Emily Willingham.