Risk of immune hemolytic anemia in children following immunization

Several case reports have described immune hemolytic anemia (IHA) following vaccination in children. We examined the risk of IHA in the 42 days following vaccination exposure using a self-controlled case series study design. In our population-based cohort of nearly 4.5 million children in the Vaccine Safety Datalink, we identified 55 confirmed cases of new-onset IHA from 1991 through 2000. We found no association between IHA and diphtheria–pertussis–tetanus vaccination (incidence rate ratio (IRR) = 0.65, 95% CI: 0.19–2.24), hepatitis B vaccination (IRR = 1.73, 95% CI: 0.59–5.01), or any vaccination (IRR = 1.04, 95% CI: 0.46–2.32).