Many parents worry about the perceived dangers of vaccines, but they often just misunderstand the facts. We’ve broken down common concerns about childhood vaccinations so you can rest easier before pediatrician appointments.

A 2019 measles outbreak affected more than 1,000 people across the country— but it could've been so much worse. If the MMR (measles, mumps, rubella) vaccine didn’t exist, we'd have at about four million cases in the U.S. every year.

Although between 80 and 90 percent of kids receive most vaccines today, growing numbers of parents are opting out of childhood vaccinations, which increases the risk of outbreaks in their community. These parents are usually worried about the “dangers of vaccinations,” despite overwhelming evidence that the current vaccine schedule has very few risks.

"Vaccines are so effective. They take diseases like measles away. But then we forget those diseases are dangerous," says Kathryn Edwards, M.D., director of the Vanderbilt University Vaccine Research Program in Nashville.

Misinformation about vaccines also contributes to anxiety, and sorting truth from fiction isn't always easy. The misconception that the measles-mumps-rubella (MMR) vaccine might cause autism, for example, has lingered in some parents' minds for more than a decade—even though more than a dozen studies show no link between the two.

Read on to learn more about why vaccines are important, and learn where those anti-vaccine arguments actually came from.

Image zoom Gecko Studio/Shutterstock

Are There Any Dangers of Vaccinations?

Of course, all vaccinations come with some risks, but our brain has a hard time putting risk in perspective, says Neal Halsey, M.D., a pediatrician and director of the Institute for Vaccine Safety at Johns Hopkins University in Baltimore. It’s similar to how many people fear flying more than driving (since automobile travel is more common and familiar) but driving is far more dangerous.

Vaccines sometimes cause mild, short-term side effects like redness and swelling at the injection site, fever, and rash. But the most serious risks, such as severe allergic reactions, are far rarer than the diseases that vaccines protect against. For example, the Centers for Disease Control and Prevention (CDC) estimates that serious allergic reactions from any vaccine occurs in one in 1 million doses.

The benefits of vaccines—namely the fact that they protect against dangerous and deadly diseases—likely outweigh the slight risks they pose.

8 Common Concerns About Vaccinations—And Why You Shouldn’t Worry

Even with the minuscule risk of vaccines, some parents still worry. They ask "are vaccines bad?" and get caught up in the online articles arguing why you shouldn't vaccinate your child. In order to ease your concerns, we’re breaking down the perceived dangers of vaccinations to give you the lowdown on the most common fears.

"Getting too many vaccines so soon will overwhelm my baby's immune system."

The Truth: Parents born in the 1970s and 1980s were vaccinated against eight diseases. A fully vaccinated 2-year-old today, on the other hand, can beat back 14 diseases. So while kids now get more shots—especially since each vaccine usually requires multiple doses—they're also protected against almost twice as many diseases.

But it's not the number of shots that matters; it's what's in them. Antigens are the viral or bacterial components of a vaccine that induce the immune system to build up antibodies and fight future infections. The total antigens in vaccines today are a fraction of what kids used to receive—even when including combination vaccines.

Plus, babies are exposed to countless bacteria everyday, and their immune systems are already prepared to handle the antigens in vaccines, says Matthew Daley, M.D. a pediatrician for Kaiser Permanente in Colorado and a researcher who studies vaccine topics. For example, babies get exposed to bacteria whenever they suck their hands, touch the floor, and come in contact with another person. "Babies handle hundreds, if not thousands, of different germs every day. Vaccines are nothing compared to this,” Dr. Daley says.

"I'm an infectious-disease specialist, but I don't see infections in children after they've had all the routine vaccines at 2, 4, and 6 months of age, which would happen if their immune systems were overloaded,” says Mark H. Sawyer, M.D., professor of clinical pediatrics at the University of California San Diego School of Medicine and Rady Children's Hospital.

"My baby’s immune system is immature, so it's safer to delay some vaccines or just get the most important ones."

The Truth: This is the biggest vaccine-related misunderstanding among parents today, says Dr. Halsey, and it leads to prolonged periods of susceptibility to diseases like measles. In the case of MMR, delaying the vaccine by even three months slightly increases the risk of febrile seizures.

There's no proof that spacing out vaccines is safer. In fact, the recommended vaccine schedule was designed to provide the greatest possible protection for your child. Dozens of infectious-disease experts and epidemiologists from the CDC, universities, and hospitals across the U.S. closely examine decades of research before making their recommendations.

"What's in vaccines anyway? Don't they contain toxins like mercury, aluminum, formaldehyde, and antifreeze?"

The Truth: Vaccines contain mostly water with antigens, but they require additional ingredients to stabilize the solution or increase the vaccine's effectiveness.

Mercury: Parents worry about mercury because some vaccines previously contain the preservative thimerosal, which breaks down into ethylmercury. Researchers now know that ethylmercury doesn't accumulate in the body (unlike methylmercury, the neurotoxin found in some fish). Even so, thimerosal has been removed from all infant vaccines since 2001 "as a precaution," Dr. Halsey says. (Multi-dose flu vaccines still contain thimerosal for efficiency, but single doses without thimerosal are available as well.)

Aluminum: Vaccines do contain aluminum salts to enhance the body's immune response, stimulating greater antibody production and making the vaccine more effective. Although aluminum can cause greater redness or swelling at the injection site, the tiny amount of aluminum in vaccines—less than what kids get through breast milk, formula, or other sources—has no long-term effect. It has also been used in some vaccines since the 1930s. "It's in our soil, in our water, in the air. You'd have to leave the planet to avoid exposure," says pediatrician and Parents advisor Ari Brown, M.D., of Austin, Texas.

Formaldehyde: Trace amounts of formaldehyde may also be in some vaccines to inactivate potential contamination. But humans get exposed to hundreds of times more formaldehyde from other sources, such as fruit and insulation material. Our body even naturally produces more formaldehyde than what's in vaccines, Dr. Halsey says.

Antifreeze: As for antifreeze, it is simply not in vaccines. Parents may be confusing its chemical names—both ethylene glycol and propylene glycol—with the ingredients used in the vaccine-manufacturing process (such as polyethylene glycol tert-octylphenyl ether, which is not harmful).

Other Ingredients: It’s true that certain ingredients in vaccines pose some risks. Antibiotics like neomycin (which halts bacterial growth in some vaccines) and gelatin (which prevents vaccine components from degrading over time) can cause extremely rare anaphylactic reactions—but this occurs roughly once or twice per 1 million doses. Some vaccines may also contain trace amounts of egg protein, but recent studies have shown that kids with egg allergies can often still receive them.

"Vaccines don't really work. Just look at last year's flu shot!"

The Truth: The vast majority of vaccines are 85 to 95 percent effective. The flu vaccine is particularly tricky, however. Each year, infectious-disease specialists from across the world meet to predict which strains are likely to circulate during the following flu season. The vaccine's effectiveness depends on the strains they pick—and sometimes they get it wrong. Even so, vaccines have lead to far fewer deaths, hospitalizations, and disabilities from influenza and other illnesses.

"There wouldn't be 'vaccine courts' if the shots weren't dangerous."

The Truth: As safe as vaccines are, unanticipated side effects do occur very rarely, says Dr. Halsey. "And people should not have to bear the financial burden associated with that." The National Vaccine Injury Compensation Program (NVICP) provides money to parents so they can pay for the medical and other costs associated with an injury in the unlikely situation where their child experiences a severe vaccine reaction. (They also pay adults injured by vaccines.)

You may wonder, why don’t they just sue the pharmaceutical companies? That's exactly what happened in the 1980s, when the dozen companies making vaccines faced lawsuits. Most of those cases did not succeed, however; winning required parents to show that a vaccine caused a health problem because it was defective. But the vaccines were not defective; they simply carried a known risk. Still, the lawsuits took a toll. Several companies simply stopped making vaccines, leading to shortages.

"Children were being left without vaccines, so Congress stepped in,” says Dorit Reiss, a professor specializing in vaccine policy at the University of California Hastings College of Law. Congress extended protection to manufacturers so they cannot be sued in court for vaccine injuries unless the claimant went through NVICP first, which allowed them to continue producing vaccines. Congress also made it easier for parents to receive compensation.

Vaccine courts operate on a "no-fault system." Parents don't have to prove wrongdoing on the manufacturer's part and are not required to prove beyond any reasonable doubt that the vaccine caused the health problem. In fact, some conditions are compensated even though science has not shown that vaccines definitely caused them. From 2006 to 2014, 1,876 claims were paid out. That amounts to one individual compensated for every 1 million doses of vaccine distributed, according to the Health Resources and Services Administration.

"Vaccines are just a way for pharmaceutical companies and doctors to make money."

The Truth: Pharmaceutical companies certainly see a profit from vaccines, but they're hardly blockbuster drugs. It's also reasonable for pharmaceutical companies to make money from their products, just as car-seat manufacturers earn profits from theirs. Contrary to popular belief, these companies rarely receive funding from the federal government. Nearly all the money earmarked for vaccine research by the National Institutes of Health goes to universities.

Pediatricians aren't profiting from vaccines, either. "Most practices don't even make money from vaccines and often lose or break even on them," says Nathan Boonstra, M.D., a pediatrician at Blank Children's Hospital in Des Moines. "In fact, some find it too expensive to purchase, store, and administer vaccines, and have to “send patients to the county health department."

"The side effects of some vaccines seem worse than the actual disease."

The Truth: In order to get approved, vaccines must make it through all four phases of safety-and-effectiveness testing—which takes 10 to 15 years and many studies. Each new vaccine intended for children is first tested in adults, then in children. All new brands and formulations must go through the same process.

The Food and Drug Administration (FDA) then scrutinizes the data to ensure the vaccine does what the manufacturer says—and does it safely. From there, the CDC, American Academy of Pediatrics (AAP), and American Academy of Family Physicians decide whether to recommend it.

No agency or company will invest that money in a vaccine that causes worse health problems than it prevents, points out Dr. Halsey: "The diseases are all associated with serious complications that can lead to hospitalization or even death." Even chicken pox, which was common decades ago, killed approximately 100 children a year before the varicella vaccine was introduced. And it was a leading cause of necrotizing fasciitis, or flesh-eating bacterial infections.

Dr. Halsey has heard parents say that good nutrition will help their kids fight these infections, but that's often not the case. Healthy children are at risk of serious complications and death from these diseases. For example, 80 percent of chicken pox deaths occurred in otherwise healthy kids, he said.

It's true that mild and moderate side effects of vaccines—such as febrile seizure and high fever—are not unheard of. However, serious side effects are far more rare. For instance, the most serious confirmed side effect of the rotavirus vaccine is intussusception, a bowel obstruction that may require surgery and occurs once in every 20,000 to 100,000 vaccinated infants. Instead of worrying about this, consider the importance of vaccination of preventing more serious, often fatal, side effects from diseases.

"Forcing me to vaccinate is a violation of my rights."

The Truth: Every state's vaccination laws are different; requirements for immunizations kick in when it's time to attend day care, preschool, or public school. These policies exist for good reason: They protect the small percentage of children who may have a compromised immune system or for whom vaccines may not work. And many of these diseases are highly contagious, meaning they'll spread quickly in schools, says Dr. Daley. He mentions measles and influenza as examples.

Every state allows exemptions if children have a medical reason for not vaccinating, such leukemia or a rare immune disorder. What's more, all states allow religious and/or personal-belief exemptions with varying requirements, except for California, Maine, Mississippi, New York, and West Virginia. Meanwhile, the exemption rates—and the disease rates—are higher in those states where it's easier for children to be granted an exemption.

Dr. Daley says that herd or community immunity might also encourage people to get vaccinated. Basically, "if enough people are vaccinated, then these infectious diseases don't spread from person to person," says Dr. Daley. This way you protect even the elderly, babies, and those with compromised immune systems.