Autism link to vaccines dispelled by a large review of studies

By Dr. Ananya Mandal, MDAug 26 2011

According to a report issued by the US Institute of Medicine (IOM), vaccines are largely safe, and do not cause autism or diabetes. This conclusion followed a review of more than 1,000 published research studies.

Ellen Wright Clayton, chairwoman of the reporting committee and director of the Center for Biomedical Ethics and Society at Vanderbilt University in Nashville, Tennessee said, “We looked very hard and found very little evidence of serious adverse harms from vaccine…The message I would want parents to have is one of reassurance.”

This report was commissioned in 2009 by the US Health Resources and Services Administration. It covers the eight vaccines that comprise the majority of claims filed with the National Vaccine Injury Compensation Program (VICP), which compensates people for adverse health effects from any of 11 vaccines. The eight vaccines under review were those for chickenpox; influenza; hepatitis B; human papillomavirus; diphtheria, tetanus and pertussis (DTaP); measles, mumps and rubella (MMR); hepatitis A; and meningococcal disease.

The report says that the evidence “convincingly supports a causal relationship” for only 14 specific adverse effects, including a range of infections associated with the chickenpox vaccine; brain inflammation and fever-induced seizures related to the MMR vaccine; allergic reactions to six of the vaccines and fainting or local inflammation caused by injection of any of them. The report noted that many of the more serious events, such as those linked to the chickenpox and MMR vaccines, only occur in children with weakened immune systems. The report also includes less-convincing evidence of links between four other adverse events and particular vaccines.

On 135 other possible links between the vaccines and adverse effects, the panel concluded that there was “inadequate evidence to accept or reject a casual relationship”. The VICP could use this information to update its Vaccine Injury Table, which already includes most, but not all, of the adverse effects listed in the IOM report.

Many children injured by vaccination have an immune or metabolic problem that is simply made apparent by vaccines. “In some metabolically vulnerable children, receiving vaccines may be the largely nonspecific ‘last straw’ that leads these children to reveal their underlying” problems, the report stated.

For instance, recent studies have found that many of the children who suffered seizures and lifelong problems after receiving the whole-cell pertussis vaccine, which is no longer used but once routinely caused fevers in children, actually had Dravet syndrome, a severe form of epilepsy. In retrospect, the whole-cell pertussis vaccine may have played little role in the underlying illness in many of these children other than to serve as its first trigger.

The committee found that evidence “favors rejection” of discredited reports that have linked the MMR vaccine to autism and, along with the DTaP vaccine, to type 1 diabetes. “We found five really solid epidemiological reports that were very clear that MMR is not associated with autism, and does not cause autism,” Wright Clayton said.

A 1998 paper by Andrew Wakefield — a UK surgeon who has now been struck off the medical register — that posited a link between vaccines and autism was retracted last year by The Lancet. The journal noted that “several elements” of the original paper were “incorrect”. However some parents who still believe there is a connection refuse or delay vaccinations for their children, leading to outbreaks of diseases such as measles and whooping cough.

Sallie Bernard, president of SafeMinds, a group that contends there is a link between vaccines and autism, said the latest report from the Institute of Medicine excluded important research and found in many cases that not enough research had been done to answer important questions. “I think this report says that the science is inadequate, and yet we’re giving more and more vaccines to our kids, and we really don’t know what their safety profile is,” Ms. Bernard said. “I think that’s alarming.”

“For those parents who are on the fence, this will be another piece of reassuring evidence, although I don't know how many more pieces of reassuring evidence you need,” says Paul Offit, chief of the infectious diseases division of The Children's Hospital of Philadelphia in Pennsylvania. “For those who are committed to the concept that vaccines are harmful independent of what the data say, it won't matter.”