Environment

Immunizations

Is There A Link Between MMR Vaccine
And Autism?…

In recent years, some parents have become concerned that the vaccine used to prevent measles, mumps, and rubella (German measles), called the MMR vaccine, might cause autism. To see whether there is truth to these concerns, researchers in Denmark studied records of all children born in that country between 1991 and 1998. Using various information sources, the researchers were able to link birth records, vaccine records, and records of diagnoses that include autism.

Over half a million children were studied; 82% of them received the MMR vaccine and 18% didn’t. The authors then looked to see whether the risk of autism was any higher among the group of children who had received the vaccine. Careful analysis indicated that autism was no more common among the children who received the vaccine. In addition, there was no link to autism when the authors took into account the age at the time of vaccination, the time since vaccination, or the date of vaccination. The authors conclude that "this study provides strong evidence against the hypothesis that MMR vaccination causes autism." (Madsen KM et al: New England Journal of Medicine, November 7, 2002, pp. 1477-1482)

In a somewhat similar approach, researchers in Finland linked MMR vaccination records with hospital records for 535, 544 children who were vaccinated in 1982-1986, when the children were between the ages of 1 and 7 years. These authors found no increased risks for neurologic disorders (like encephalitis) in the three months following vaccination, and they also found no increase in hospitalizations for autism following vaccination. (Makela A et al: Pediatrics, November, 2002, pp. 957-963)

...And An Expert’s Commentary

In a commentary accompanying the Danish study, Dr. Edward Campion notes that "this careful and convincing study shows that there is no association between autism and MMR vaccination. Other studies also found no association." Unfortunately, he points out, "Strongly held beliefs are difficult to change. We live in an era in which the public does not have a high degree of trust in the vaccine manufacturers, the government, or the medical establishment. Consumers have become highly sensitive about safety, and their confidence has not been bolstered by recent …controversies such as that over mercury-containing preservatives in vaccines (thimerosal, which has now been removed)." (Campion EW: New England Journal of Medicine, November 7, 2002, pp. 1474-1475)

COMMENT: These two studies together provide experience on over one million children, and the failure to find any link to autism, coupled with earlier good studies that also found no link, raises questions about why the link was suggested in the first place. The original suggestion came from a group of researchers in the United Kingdom who were conducting studies on a very small group of children who had chronic intestinal problems and behavioral abnormalities. Based on findings that had nothing directly to do with the MMR vaccine, they speculated that measles vaccine could cause such problems, including autism. This theory made sense to a number of parents whose children were diagnosed with autism shortly after getting an MMR shot. Soon the idea was picked up by the Internet and by other parties who were suspicious of vaccines in general, and what started as speculation based on poor science turned into something that made many parents anxious and concerned.

How do these new studies ex-plain the timing some parents report between the vaccine and their child’s autism? Autism is a condition that frequently shows up in infants, and the MMR vaccine is a vaccine that is typically given to infants. Since almost all children in the U.S. get MMR vaccine, those who develop autism also will have been vaccinated. When we consider that many millions of children receive the MMR vaccine, we can expect, by chance alone, that some of those children who develop autism will be diagnosed within a few months following their shot, just as some will be diagnosed a few months before their shot (this is what the Danish study found).

So after so much concern was raised about the safety of the MMR vaccine, these studies offer what most would consider the definitive reassurance that MMR vaccine is not a cause of serious neurologic problems, including autism.