Immunization Safety Review: Vaccinations and Sudden Unexpected Death in Infancy


With current recommendations calling for infants to receive multiple doses of vaccines during their first year of life and with sudden infant death syndrome (SIDS) the most frequent cause of death during the postneonatal period, it is important to respond to concerns that vaccination might play a role in sudden unexpected infant death.

A death that occurs suddenly and unexpectedly in the first year of life, whether or not there is an underlying disorder that predisposes to death, has been referred to by the term "sudden unexpected death in infancy" (SUDI). SUDI includes deaths that can be attributed to identifiable causes and deaths for which the causes remain uncertain. SIDS is the diagnosis most commonly given to the deaths of uncertain cause. The committee reviewed epidemiologic evidence focusing on three outcomes: SIDS, all SUDI, and neonatal death (infant death, whether sudden or not, during the first 4 weeks of life).

Based on this review, the committee concluded that the evidence favors rejection of a causal relationship between some vaccines and SIDS; and that the evidence is inadequate to accept or reject a causal relationship between other vaccines and SIDS, SUDI, or neonatal death. The evidence regarding biological mechanisms is essentially theoretical, reflecting in large measure the lack of knowledge concerning the pathogenesis of SIDS. Anaphylaxis related to vaccination has been discussed in detail in previous IOM reports and is reexamined in the report; the committee observed that anaphylaxis is known to be a rare but causally related adverse event following the administration of some vaccines. Fatal anaphylaxis in infants is extraordinarily rare.

The committee found no basis for a review of current immunization policies, but saw a clear need for continued research on adverse event following vaccination and on the biological basis for sudden unexpected infant deaths.