WASHINGTON -- There is no evidence of a link between crib death -- known as sudden infant death syndrome -- and multiple vaccines given in infancy, a study concludes.

Many parents became concerned about vaccines after an Australian researcher in the 1980s argued that there was a connection. But an Institute of Medicine report Wednesday reinforces previous studies that found no relationship between the vaccines and 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," said Marie McCormick, head of the committee that wrote the report.

The National Center for Health Statistics recorded 2,523 SIDS deaths in the United States in 2000, the most recent data available. That compares with 5,417 in 1990. SIDS deaths have declined in recent years following a campaign to instruct adults to place babies on their backs while they sleep and to avoid soft bedding materials that could interfere with babies' breathing.

The available data do not answer all possible questions about SIDS and vaccines, said McCormick, head of the department of maternal and child health at Harvard School of Public Health.

"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," she said.

Most American children during their first 12 months get several vaccines, including the combined diptheria-whooping cough-tetanus vaccine and immunizations against influenza, hepatitis B, polio and pneumococcal bacteria. Whooping cough is also known as pertussis.

While the study cleared the vaccines from causing SIDS, it did note that an older form of the diptheria-pertussis-tetanus vaccine had been related to two 1946 cases of severe inflammatory reaction known as anaphylaxis.

That vaccine is no longer given to infants.

The report notes that medical experts have not reached agreement on how SIDS occurs. SIDS is the diagnosis most often used in cases of infant death without warning for which no cause is identified.

The campaign to have babies placed on their backs to sleep is based on the theory that their position may contribute to SIDS. Other possibilities are an underlying physical problem during a critical development period or exposure to some outside trigger.

Some research suggests that an abnormal immune response to common respiratory bacteria or viruses may be a factor in SIDS. But the committee said there are no studies demonstrating the ability of vaccines to lead to that kind of inflammation.

In addition to concluding that SIDS is not related to multiple vaccine doses, the study reaffirmed previous findings that SIDS is not linked to the older diptheria-pertussis-tetanus vaccine. Because the current DPT vaccine has fewer side effects than the older one, the committee found no reason to suspect any link to it either.

There was not enough evidence to determine whether relationships exist between other individual vaccines and SIDS, the committee said.

The report, the sixth in a series on vaccine safety, found there is not enough evidence to determine if the hepatitis B vaccine, the only vaccine given to newborns, is linked to newborn deaths. That vaccine is often given later with other vaccines, unless the mother has hepatitis.

The Institute of Medicine is a private institution that provides health policy advice under a congressional charter granted to the National Academy of Sciences.