Can vaccines cause SIDS/SUDC?

The short version: the evidence on vaccines and SIDS is split between large studies showing no increased risk and case reports showing deaths with biological markers of a shock reaction.

The largest studies, a 2007 meta-analysis of nine case-control studies and a 2007 German study of 307 SIDS cases, found that vaccinated infants had a lower risk of SIDS than unvaccinated infants [1, 4]. The German study reported a multivariate odds ratio of 0.51 (95% CI 0.25-1.00), meaning vaccinated infants were about half as likely to die of SIDS [1]. The meta-analysis found a similar pattern across all nine studies [4]. These are the studies the establishment points to.

But there is a second body of evidence that does not fit that picture. A 2008 forensic case report described a 3-month-old infant who died within 24 hours of a hexavalent vaccine with a serum beta-tryptase level of 43.3 mg/L (normal under 10) and mast cell counts three times higher than controls [2]. A 2006 case series reported six infants who died shortly after hexavalent vaccination, with tryptase levels as high as 108 in some cases [3]. Elevated tryptase is a marker of mast cell degranulation, which can trigger shock and respiratory failure. A 2006 study of preterm infants found that after DTP-IPV-Hib immunization, 45% had an increase in apnea, bradycardia, or desaturations, compared to 29% in controls (odds ratio 2.41, 95% CI 1.3-4.5) [7].

The conflict matters because the large studies have a design problem. They compare vaccinated infants to unvaccinated infants, but the unvaccinated group includes infants who were too sick to be vaccinated or who died before their scheduled shots. That is called healthy vaccinee bias: healthier infants get vaccinated, so the vaccinated group looks healthier by selection, not because the vaccine protects them. The German study tried to adjust for this with multivariate analysis, but the odds ratio still crossed 1.0 at the upper end of the confidence interval [1].

The mechanism is biologically plausible. The spike protein and aluminum adjuvants can destabilize the colloidal charge of blood, triggering mast cell degranulation and microvascular sludging. In a vulnerable infant, especially one with a genetic predisposition to hyperinflammatory responses (the IL-1RN 2/2 genotype was associated with a 4.8-fold increased risk of unexplained SUDI in one study [6]), this could tip into fatal shock.

My call: the evidence does not prove that vaccines cause SIDS, but it also does not prove they are safe. The large studies are weakened by healthy vaccinee bias, and the case reports document a plausible mechanism that the establishment has not adequately investigated. The most informative study, a prospective comparison of vaccinated versus unvaccinated infants with full autopsy and tryptase measurement, has never been done. Confidence: low.