March 6, 2001 (Washington) -- Researchers continue to search furiously for any clues linking the measles-mumps-rubella (MMR) vaccine and autism, but in the latest study to weigh in on the issue, they report that the vaccine poses little, if any, risk. While looking at trends in vaccine use, they found that although the rate of autism increased almost fourfold during a 14-year period, use of the MMR vaccine increased only slightly during this time period.
Because the study looked at cases of autism after they were reported rather than when they were diagnosed, the researchers could not completely rule out the vaccine as one possible cause. "But supposing the connection is real and the vaccine is one of the causes, these data show it could not be a major contributor," lead author Loring Dales, MD, MPH, an epidemiologist and the principal researcher, tells WebMD.
Autism is a disorder of brain development that is characterized by problems with social interaction, communication skills, a strict routine, and the need for repetitive behavior, such as swaying or watching the same video over and over again. There is no cure, but intensive education can help autistic children develop new skills. Unfortunately, these programs are expensive and can cost anywhere from $8,000 to $100,000 a year for a residential school setting.
But for parents with newly diagnosed children, these day-to-day challenges and expenses are not the only hurdles they must overcome. Often, parents of autistic children also must deal with the simple frustration of not knowing why their child is autistic.
To investigate the possible connection, Dales and two of his colleagues at the California Department of Health compared 15 groups of children born between 1980 and 1994. During that period, California experienced a marked increase in the number of reported cases of autism, from 44 cases for every 100,000 live births in 1980 to about 208 cases for every 100,000 live births in 1994.
This is a relative increase of about 373% in the number of autism cases, but Dales says the researchers found that the concurrent increase in the state's MMR immunization rate was significantly smaller, only 14%.
For supporters of the MMR vaccine, the current study available in the March 7 issue of the Journal of the American Medical Association could not have come at a better time.
The Institutes of Medicine is scheduled this week to once again review the possible connection between autism and the MMR vaccine. Once the IOM completes this review, which it began in January, it will then advise U.S. health authorities on what course of action they should take in terms of recommending the childhood vaccination.
The fear among some parents and researchers that the vaccine might trigger autism is largely due to the apparent increase in autism cases since the introduction of the MMR vaccine. But to date, there is no evidence to clearly establish a causal link between the MMR vaccine and autism.
In 1998, Andrew Wakefield, MD, an expert in bowel diseases at the Royal Free Hospital School of Medicine in London, speculated that the MMR vaccine damages the bowel, causing autism.
Wakefield's theory: The MMR vaccine damages the bowel. A damaged bowel cannot properly digest essential vitamins and nutrients needed for normal development. A damaged bowel also would be unable to filter out toxic materials that could harm the brain.
Other researchers now say that they too have established that autistic children have a larger number of antibodies to measles in their brains than their peers, suggesting that the MMR vaccine may travel to the brain where it could cause further damage.
Among those researchers is Vijendra Singh, PhD, a research professor at Utah State University in Logan.
"Based upon my research, there is a good possibility that the MMR vaccine might be the culprit," Singh told WebMD in a recent interview. "I cannot conclusively say that I have found a fundamental cause. But this is good science. It should not be ignored."
The majority of experts disagree. The mainstream thought is that the increase in reported cases of autism is due to experts' recent adoption of a broader definition of the disorder rather than the introduction of the MMR vaccine.
Although the diagnosis usually is made shortly after the vaccine is administered, trained experts frequently can make the diagnosis at a much earlier age, Paul Offit, MD, chief of infectious disease at the University of Pennsylvania School of Medicine, tells WebMD.
Although the California study does not address why that state is suffering from a rise in autism cases, the findings can still be generalized because this study duplicated the results of similar studies conducted elsewhere, such as in the U.K., Dales says.
"All of these studies have found the same results. So it sounds like these results can be generalized," he tells WebMD.
The California study, though, is unlikely to convince all the critics of the vaccine, some of whom believe that U.S. health authorities have decided to ignore this connection because of the vaccine's perceived benefits.
The CDC maintains that the MMR vaccine is of significant benefit. In just one decade, the agency says, the MMR vaccine has managed to reduce the number of measles cases from more than 27,000 a year to a mere 100 a year. During that time frame, the number of reported deaths also has decreased from more than 50 a year to none, the agency says.
Still, the view that these benefits do not justify ignoring the possible connection between the vaccine and autism has engendered some powerful allies. Among those is U.S. Rep. Dan Burton, (R-Indiana), whose grandson is autistic.
Last April, Burton held an emotionally charged congressional hearing that some insiders believe fueled the IOM investigation. The IOM often consults members of Congress on medical issues.
The IOM has denied this connection. The level of concern simply has made it imperative that the IOM address this issue, Kathleen Stratton, PhD, who co-chairs the IOM committee, told an industry group last year.
The IOM vaccine committee investigating the MMR-autism connection will meet once more this year, and over the course of the next three years, address eight other vaccine-related safety concerns. The National Institutes of Health and CDC are jointly funding the entire project.