Experts Say Benefits Are Proven, Risks Are Not

June 12, 2002 -- Despite overwhelming scientific evidence in favor of the safety of the MMR vaccine, some controversial research has raised questions about a possible link between this common childhood vaccine and developmental disorders such as autism. But now there is even more reason for parents to feel confident about the safety of the MMR vaccine.

The latest dose of reassurance comes from a comprehensive review of the research on the MMR vaccine and its benefits and potential risks.

In their report, Anna Donald, MD, and Vivek Muthu, MD, of Bazian Ltd, an independent healthcare research group in London, analyzed the most significant studies on both the MMR -- measles, mumps, and rubella -- and single measles vaccination. They found no scientific evidence that MMR or the measles vaccine is associated with autism.

The researchers say the study clearly shows, however, that the vaccine virtually eliminates the risk of measles and measles complications, which can include pneumonia, brain damage, dementia, or even death in about 6% of those who become infected with the highly contagious virus.

The team found only a slight risk of fever (which resolved by itself within three weeks) following vaccination. But they say that the risk of this slight fever is minimal compared with the dangerously high fever that occurs in all children who develop measles.

The report is published in the current issue of the journal Clinical Evidence.

Addressing the Controversy

The review also looked at a controversial British study published in 1998 by Andrew Wakefield, MD, which raised the question of potential link between MMR and a developmental disorder in 12 children with inflammatory bowel syndrome.

The authors concluded that the Wakefield study was too small and, does not establish MMR as a cause of inflammatory bowel disease, autism, or child developmental [problems]."

Samuel Katz, MD, chairman emeritus of the department of pediatrics at Duke University Medical Center, says the Wakefield study has been seized upon by families who have children with autism as a means to explain an unexplainable illness -- even though several major reviews of the research on the issue have found no evidence of a link between the vaccine and autism.

"The time relationship is a difficult one. Autism very commonly becomes apparent in the second year of life, and that's when you're giving MMR," says Katz, who also helped develop the measles vaccine now used worldwide.

Sorting Scientific Fact From Fiction

"These are epidemiological studies. That is, they are looking at large numbers of children and sorting out the numbers who develop autism and who did or didn't have the [MMR] vaccine," says Katz. "That's fine from the point of view of statistics and numbers, but those who are convinced that MMR has something to do with autism need the scientific proof."

That's why Katz says several studies are being organized and are underway by the National Institutes of Health, the CDC, and the American Academy of Pediatrics that will address those issues more fully. But he also points out that no other research has been able to duplicate the findings of the Wakefield study, despite several attempts.

Kathleen Stratton, PhD, senior program officer in the division of health promotion and disease at the Institute of Medicine, a division of the National Academy of Sciences, says sorting out the scientific facts about the safety of vaccines in a practical way that parents can understand is one of the biggest challenges researchers face.

"We would love to know how to say it better," says Stratton. "For some people, the scientific glass is always half empty."

Stratton says healthcare providers should prepare parents and explain what is known about the benefits and possible risks of vaccination before their baby is born.

"There is not a debate about the benefits of these vaccines. There is uncertainty about many of the risks," Stratton says.

Katz and Stratton spoke at a briefing today on vaccine safety sponsored by the March of Dimes.