The UK accelerated immunization programme and sudden unexpected death in infancy: case–control study.

Abstract

Objectives To investigate whether the accelerated immunization programme in the United Kingdom is associated, after adjustment for potential confounding, with the sudden infant death syndrome.Design Population‐based case–control study, February 1993 to March 1996. Parental interviews were conducted for each death and for four controls matched for age, locality and time of sleep. Immunization status was taken from records held by the parents.Setting Five regions in England with a combined population of over 17 million.Subjects Immunization details were available for 93% (303/325) of infants whose deaths were attributed to the sudden infant death syndrome (SIDS); 90% (65/72) of infants with explained sudden deaths; and 95% (1515/1588) of controls.Results After all potential confounding factors were controlled for, immunization uptake was strongly associated with a lower risk of SIDS [odds ratio 0.45 (95% confidence interval 0.24–0.85)]. This difference became non‐significant [0.67 (0.31–1.43)] after further adjustment for other factors specific to the infant's sleeping environment. Similar proportions of SIDS deaths and reference sleeps (corresponding to the time of day during which the index baby had died) among the controls occurred within 48 hours of the last vaccination [5% (7/149) versus 5% (41/822)] and within 2 weeks [21% (31/149) versus 27% (224/822)]. No longer term temporal association with immunization was found (p = 0.78). Of the SIDS infants who died within 2 weeks of vaccination, 16% (5/31) had signs and symptoms of illness that suggested that medical contact was required, compared with 26% (16/61) of the non‐immunized SIDS infants of similar age. The findings for the infants who died suddenly and unexpectedly but of explained causes mirrored those for SIDS infants.Conclusions Immunization does not lead to sudden unexpected death in infancy, and the direction of the relation is towards protection rather than risk. More reassuring information about the safety of the accelerated course of immunization. This paper should help us reassure the public that young babies' immune systems are not too immature to handle multiple vaccines. In fact there is no logic to this view at all: Babies' immune systems are set up to be able to respond to multiple challenges, and there is mounting evidence that the lack of such challenges has its own deleterious effects on the subsequent development of the immune system.This paper also addresses some of the research into babies’ temperature control, which suggested that the response to immunization at this age might precipitate an abnormal response in some babies. Epidemiologically, there seems to be no risk of death. The authors postulate a possible protective effect, but I think that residual confounding may account for this, despite their best efforts to avoid it.