Vaccines do not cause autism

The study by the Institute of Medicines at the US National Academy of Sciences, which reviewed more than 1,000 research papers, is widely seen as reassuring confirmation of the safety of vaccination.

Vaccines cause very few side effects, according to the authors, and the majority of those that do occur are brief and self-limiting such as fever and seizures.

The study was funded by the US Department of Health and Human Services amid concern that misplaced fears over vaccine safety are causing a decline in immunisation rates.

Health officials across the world have repeatedly reassured the public that vaccines are generally safe. However, vaccine uptake rates remain too low in some countries – the importance of which has, for example, been highlighted by measles outbreaks in Europe this year.

The panel looked at eight common vaccines: the combination measles-mumps-rubella (MMR), the diphtheria-tetanus-acellular pertussis (DTaP), varicella for chickenpox, influenza, hepatitis B, meningococcal, tetanus-containing vaccines, and the human papillomavirus (HPV) vaccine.

These vaccines protect against a host of diseases, including measles, mumps, rubella, whooping cough, hepatitis, diphtheria, tetanus, chickenpox, the flu, meningitis and pneumococcal disease and cervical cancer.

The expert who chaired the panel was Prof Ellen Wright Clayton, professor of pediatrics and law, and director of the Center for Biomedical Ethics and Society at Vanderbilt University in Nashville. She said side effects are generally mild and highlighted the risk of not being vaccinated.

“Despite looking very hard, it was really hard to find that vaccines cause injuries and the injuries they do cause are generally pretty mild and self-contained,” she said.

MMR-autism link debunked – again

Prof Clatyon said the expert panel had found – once again – that the MMR vaccine does not cause autism.

“The DTaP vaccine, which is the pertussis vaccine, does not cause type 1 diabetes, and the killed flu vaccine does not cause Bell’s palsy (temporary facial paralysis) and it doesn’t make your asthma get worse,” Clayton said.

“The evidence was really quite strong that vaccines don’t cause these side effects,” she told news agencies.

Side effects are real but rare

MMR can cause a rare form of brain inflammation in some people with severe immune system deficiencies, the panel noted.  With the varicella vaccine against chickenpox, some people can develop brain swelling, pneumonia, hepatitis, meningitis or shingles, but this again occurs most often in people with compromised immune systems.

Six vaccines – MMR, varicella, influenza, hepatitis B, meningococcal, and the tetanus-containing vaccines – also exceptionally can trigger anaphylaxis, an allergic reaction that appears shortly after injection.

But Clayton said this can be addressed with the requirement by doctors to have vaccine patients remain in the waiting room for 15 minutes after their shot to make sure they do not have any allergic reaction.

Is evidence enough?

This is certainly not the first time that scientists have flatly rejected claims that vaccines are often linked to autism and diabetes. However, these myths have proven stubbornly difficult to beat.

Anti-vaccine campaigners have already questioned the findings of the Institute of Medicine report, with one critic – Marisa De Lisle, a US-based chiropractor – telling the Seattle Times that the review merely highlights a lack of evidence. “Just because there is no evidence, that doesn’t mean it’s safe,” she said.

Meanwhile, groups such as Age of Autism criticised the methodology of the Academy of Sciences expert panel and urged parents to “educate themselves” by reading anti-vaccination books instead.

As noted by Dr Heidi Larson in a Vaccines Today guest editorial earlier this month, hard data alone does not convince some people. She called for more research into the complex factors which contribute to public trust in vaccines.

In a separate with Vaccines Today, Seth Mnookin – author of The Panic Virus ­– suggested a combination of science and storytelling is essential to communicating with the minority of parents who remain so sceptical of vaccines that they refuse to have their children immunised.

The new study is an unequivocal boost for vaccination, even if it simply reiterates what was already known. The next step is to engage with those for whom science alone is not enough.

Read our Vaccine Facts article Do vaccines cause autism?

External links

Nature News: Vaccines given a clean bill of health

New York Times: Vaccines cleared again as autism culprit

Reuters: Vaccines largely safe, US expert panel finds

Washington Post: ‘Vaccines are generally safe’, National Academy of Sciences says

Boston Globe: Few risks are linked to vaccines, US committee finds

Seattle Times: Thorough study likely won’t put vaccine worries to rest