March 13, 2003 -- The only link between sudden infant death syndrome (SIDS) and childhood vaccines is timing, according to a major new report. Researchers say that SIDS deaths may occur at a time that infants are given multiple vaccines, but there is no evidence to suggest that the vaccines themselves increase the risk of SIDS.
The report, released this week by the Institute of Medicine, reviewed recent studies on the issue. The researchers say there are no data to support that the diphtheria, tetanus, and whole-cell pertussis (DTwP) vaccine or exposure to multiple childhood vaccines cause SIDS.
"Although the timing of infant vaccinations coincides with the period when SIDS is most likely to occur, parents should rest assured that the number and variety of childhood vaccines do not cause SIDS," says Marie McCormick, MD, ScD, chairwoman of the committee that wrote the report and professor at the Harvard School of Pubic Health, in a news release.
SIDS is the most common cause of death for infants less than a year old. By definition, it describes a sudden death of an infant that cannot be explained by other causes. Although some factors are thought to increase the risk of SIDS, such as putting an infant to sleep on his or her stomach, the exact cause is unknown.
Researchers say that it has been suggested that an abnormal immune response to common bacteria or viruses that affect the lungs might be a factor in SIDS. But there are no studies that show vaccines might induce such a response. The committee says the ability of vaccines to act as triggers of SIDS is only theoretical.
"We do not have the data that would definitively answer all questions about links between vaccines and SIDS and other forms of sudden, unexpected death in infancy," says McCormick. "However, we believe that the data we do have, along with the increasing rarity of these kinds of infant deaths, make a review of the vaccine schedule unnecessary."
The current vaccine schedule calls for infants to receive five vaccines to protect against seven infectious diseases before age 1.
The report also looked at the potential link between vaccines and other sudden unexpected deaths in infancy, which, unlike SIDS, includes infant deaths for which there may or may not be a clear cause of death.
The committee found that only an older vaccine against diphtheria and pertussis that is no longer used was related to a very rare and severe inflammatory reaction known as fatal anaphylaxis. Only one such case was documented in 1946, and they say there have been no other cases of infant deaths causes by anaphylaxis following vaccination in the 57 years since.