Report: Vaccines Don't Cause Autism, Only Rarely Have Serious Side Effects

Experts conclude that vaccines are mostly safe, but that won
Experts conclude that vaccines are mostly safe, but that won

By Karen Weintraub
Guest Blogger

A federal report released today concludes that the health benefits of childhood vaccines vastly outweigh the rare chance of serious side effects. But the report will likely do little to allay the fears of a minority of parents who believe, despite scientific evidence, that vaccines are linked to disorders such as autism.

The problem, as the researchers themselves admit, is that it’s impossible to prove a negative – that vaccines don’t ever cause autism, for instance. Plus, the new report is an analysis of 1,000 existing studies on vaccines, so it puts existing information in context rather than adding new data to the debate.

Those who raise concerns about vaccines say that new research is needed to look at whether the shots can cause problems in subgroups of children – perhaps groups that are too small to have been picked up by existing studies.

Still, the 635-page report concludes that common childhood vaccines are extremely safe and effective at preventing measles, mumps rubella, tetanus, diphtheria, pertussis, polio, chicken pox, flu, meningitis, hepatitis and human papilloma virus, which can cause cancer.

“We have a lot of evidence that vaccines save lives and avert a lot of suffering,” Dr. Ellen Wright Clayton, the chairwoman of the panel that wrote the report, said in a news conference today. “The side effects we’re talking about here are really relatively rare – because it’s hard to find them when you look at a general population. The majority of the ones we found are either short-term or readily treated.”

She also spoke out clearly against some of the biggest worries parents have about vaccines.

“The MMR vaccine does not cause autism,” said Clayton, a professor of pediatrics and law, and director of the Center for Biomedical Ethics and Society at Vanderbilt University in Nashville, Tenn. “MMR and DTaP do not cause Type 1 diabetes. The flu shot does not cause Bell’s palsy and does not trigger episodes of asthma.”

In writing the advisory report, Clayton led a team of scientists from multiple disciplines, including pediatricians, statisticians and infectious disease experts.

The team’s analysis will be used by the National Vaccine Injury Compensation Program, which oversees claims from people who have been injured by vaccines. A tax on vaccines pays for a fund to compensate proven vaccine injuries. (The program has paid out $2 billion to compensate 2,500 families since 1989. More than 2,400 people filed claims in 2003 claiming their child’s autism was triggered by a vaccine, but because most had failed, by last year, only 18 families filed such claims, program statistics show.)

Among the report’s other findings:

Most vaccines, in rare cases, can cause anaphylaxis, an immediate and extreme allergic reaction, possibly because the vaccines are often made with eggs and other allergens.
Roughly 1 out of every 4,000 children vaccinated against MMR will suffer a febrile seizure, usually within 8-14 days after vaccination. Febrile seizures generally do no long-term damage to the child’s brain and do not predispose the child to epilepsy.

Some children with existing though possibly undiagnosed immunological problems will develop chicken pox from the varicella vaccine, because, like the oral polio vaccine, it is a live virus vaccine. Most of the other vaccines (including the polio vaccine administered as a shot) are not live viruses and so cannot transmit the disease they are meant to prevent. Even if the vaccine does cause this rare response, it saves many more children from dying of chicken pox, according to a recent study, Clayton said, and some children with immune problems fare far better with vaccines than they would if they got the actual disease.

There is very little long-term data on the HPV vaccine, which was introduced in 2006, but Clayton said so far, the vaccine’s safety profile is extremely good. “It certainly didn’t show anything that was alarming so far,” she said.

Clayton says she is concerned that some parents will continue to doubt vaccine safety. But she said those worried about possible damage from vaccines should remember the very real dangers of the diseases those shots are meant to prevent.

“People forget what these diseases are like. When I was a resident we had a child with tetanus. You don’t want that to happen,” she said. “Vaccines are a victim of their own success in this regard.”

Unfortunately, because there was no new research in this report, people who have already made up their minds won’t be changed by it.

Perhaps some people will never be convinced that vaccines are as good as they could be. Or maybe, it would be worthwhile to do a few more studies aimed at addressing the concerns of parents whose kids developed autism symptoms shortly after routine vaccines. What do you think?

Karen Weintraub is a freelance Health & Science writer based in Boston.

This program aired on August 25, 2011. The audio for this program is not available.

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Rachel Zimmerman Reporter
Rachel Zimmerman previously reported on health and the intersection of health and business for WBUR. She is working on a memoir about rebuilding her family after her husband’s suicide. 



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