News

US report finds no link between MMR and autism

Charles Marwick, Washington, DC

A new report from the US Institute of Medicine has rejected an association between autism and childhood immunisation with the MMR (measles, mumps, and rubella) vaccine.

Dr Marie McCormick, chairwoman of the committee that drafted the report, said that on the basis of the evidence "no change in MMR immunisation procedures is warranted at present." Dr McCormick, professor of maternal and child health, Harvard School of Public Health, Boston, spoke at a press conference held by the institute as the report was released.

In one of the more strongly worded statements on the issue to have appeared since the association between MMR vaccine and autism was first suggested, the report cites the lack of epidemiological evidence showing an association and insufficient data from case reports, including the initial 1998 report in the Lancet (1998;35l:637-41), to either prove or disprove causality. It also describes the biological models linking MMR vaccine to autism as fragmentary.

The committee weighed evidence from at least nine studies since the initial 1998 report reviewing the association between MMR vaccine and autism.

At the same time, the institute's report said that it did not exclude the possibility that MMR vaccine could, in rare cases, contribute to what it terms "autistic spectrum disorders." It goes on to note the high level of concern about the safety of MMR vaccine and that this must be addressed. "There is need for continued attention to this," said Dr McCormick.

The report made it clear that the benefits of immunisation far outweighed any risk associated with MMR vaccination. "No vaccine is 100% safe," said Dr McCormick, but she noted that, if left unchecked, diseases such as measles, mumps, and rubella could cause considerable sickness and death.

The report noted that before the vaccine was introduced in 1963 there were four million cases of measles reported annually in the United States; in 1999 there were only 100 reported cases. Before 1963, complications from measles were common: annually there were 150000 cases of respiratory complications, 100000 cases of otitis media, 48000 admissions to hospital, 7000 cases of seizures, and 4000 cases of encephalitis; overall, an estimated 4000 to 8000 deaths from measles complications occurred annually.

Immunization Safety Review: Measles-Mumps-Rubella Vaccine and Autism is available on the internet (www.nap.edu).