Myth or Fact: 6 Things You Need to Know About Vaccines

No, immunizations aren't linked to autism.

Medically reviewed in December 2021

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The number of pediatricians that encountered parents who refused vaccinations for their children jumped from 75 percent in 2006 to 87 percent in 2013, according to data from the American Academy of Pediatrics.

Parents declined or postponed vaccinations for two main reasons, according to the study. Those who declined believed the vaccines were unnecessary, and those who delayed did so to prevent their child from being uncomfortable or because they incorrectly believed multiple vaccines would overwhelm their young one's immune system.

Staying up to date with your child’s immunizations is an important part of keeping kids—and their peers—safe from life-threatening infectious diseases. Here's the truth behind six of the most common immunizations myths.

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Myth #1: Vaccines cause autism

Even the largest and most in-depth studies have yet to prove a connection between vaccines and autism.

In 1998, former doctor Andrew Wakefield published a fraudulent study in The Lancet linking the measles, mumps and rubella (MMR) vaccine to autism. The study was widely discredited and retracted from publication, while Wakefield was barred from practicing medicine in the United Kingdom. Regardless, some still believe the connection.

In the years since, numerous studies from major organizations, including the World Health Organization, have shown that childhood vaccines are not harmful. Study after study has also shown that the MMR vaccine, in particular, does not cause autism in children who receive it.

In 2011, an Institute of Medicine (IOM) report, which examined eight vaccines given to both kids and adults, found that they are very safe. Then, in 2013, a CDC study examined the immune response to the vaccine in children during the first two years of life. They found no differences between kids with autism and those who did not have this condition.

More recently, a March 2019 study published in the Annals of Internal Medicine, analyzed the safety of the MMR vaccine even more rigorously. Researchers in Denmark used more children and more cases (hence more statistical power) to investigate concerns about a link between the vaccine and autism. They also included a larger number of children considered at high-risk for autism to address the specific claim that the MMR vaccines may be more dangerous for these kids.

The scientists evaluated whether the MMR vaccine increased the risk of autism in 657,461 children born in Denmark between 1999 and 2010. They tracked the kids until August 2013, documenting diagnoses of autism spectrum disorders and risk factors for these conditions, including parents’ ages, siblings with autism, method of delivery, smoking during pregnancy, preterm birth and low birth weight.

The study found no evidence of a link between the MMR vaccine and autism or an increased risk for these disorders—even among high-risk kids. 

A February 2017 study published in Nature also suggests that the brain changes related to autism begin in early infancy, before a child would be given the MMR vaccine.

Nevertheless, with increased travel to places where the vaccine is not available—and more parents opting not to vaccinate their kids—the number of measles cases is on the rise.

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Myth #2: Childhood vaccines contain mercury (thimerosal)

Thimerosal, a mercury-based preservative, was removed from all childhood vaccines in 2001, according to the Centers for Disease Control and Prevention.

Thimerosal had been used to prevent the buildup of dangerous bacteria in vaccine vials. Aside from potential to cause redness at the injection site or, rarely, allergic reactions, there’s no evidence that thimerosal caused harm, even before it was removed.

It isn't the same risky kind of mercury found in certain fish (methylmercury) and it has absolutely no link to autism. In fact, thimerosal was never even in the MMR vaccine, which was the focus of Wakefield’s debunked autism study.

Today, the flu shot is the only vaccine available to kids that could contain thimerosal, but not all versions have it.

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Myth #3: Vaccines aren’t necessary

Vaccines prevent between two and three million global deaths every year, according to the World Health Organization—and an additional 1.5 million deaths could be avoided if vaccine coverage improved. Not only do immunizations help the body build a resistance to potentially fatal infectious diseases, they make a person less likely to pass those illnesses to someone else. Vaccines have virtually eradicated disease like polio and diphtheria, but we'd be remiss to think they won't reappear without continued immunizations.

Unvaccinated children and adults can spread disease to those who are too young or too medically fragile to be immunized. That means missing even one shot could not only endanger a person’s life, but the lives of those around them.

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Myth #4: Vaccines cause sudden infant death syndrome (SIDS)

In 2003, the Institute of Medicine examined the relationship between SIDS and DTwP, DTaP, HepB and polio vaccines, as well as specific combinations of inoculations. Review results suggested no association between immunizations and childhood deaths. Subsequent studies haven’t found a link, either.

Perhaps the myth began as a result of pure coincidence. Most cases of SIDS occur in infants younger than 12 months, and children can receive as many as 15 vaccinations in the first year of life.

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Myth #5: It’s not safe to give multiple childhood vaccines at one time

Evidence shows that’s not the case. Both the Advisory Committee on Immunization Practices and the American Academy of Pediatrics recommend kids receive several routine vaccines at once, as long as they have a healthy immune system.

A 2018 study published in The Journal of the American Medical Association (JAMA), suggests the delivery of multiple vaccinations does not negatively affect an infant’s immune system. The study assessed hospital visits of 944 children between the ages of 24 and 47 months who had received recommended vaccinations during their first 23 months. Research suggested early vaccinations did not lead to an increased risk of getting infections unrelated to the vaccines (such as respiratory or gastrointestinal infections).

Giving a child simultaneous vaccines, as well as combined vaccines, has its advantages, including fewer trips to the doctor’s office and a higher likelihood of completing recommended vaccines on schedule.

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Myth #6: Only kids need vaccines

If you thought vaccines were only for little ones, think again. Experts estimate more US adults die of vaccine-preventable diseases than from prostate cancer or car accidents. Here’s a rundown of the vaccines you may need as an adult:

  • Influenza: The flu shot is recommended for people six months and older.
  • Tdap: Adults need one shot of tetanus, diphtheria and pertussis vaccine (Tdap), followed by a Td or Tdap booster every 10 years.
  • Zoster: The shingles vaccine is now recommended for adults 50 years and older.
  • Pneumococcal: The pneumonia vaccine is recommended for adults 65 and older, and earlier for people with certain risk factors.

Certain adults may also need vaccines for meningitis, hepatitis, chickenpox, human papilloma virus (HPV) and other conditions. Talk with your doctor about which adult vaccines you may need.

The bottom line: Vaccines save lives.

This article was updated on August 22, 2018.

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