Breastfeeding and risk for fever after immunization.

Objective: The objective of this study was to evaluate the effects of breastfeeding on the risk for fever after routine immunizations.

Methods: A prospective cohort study was conducted at a pediatric vaccination center in Naples, Italy. The mothers of the infants scheduled to receive routine immunizations were instructed on how to measure and record infant temperature on the evening of the vaccination and for the subsequent 3 days. The information about the incidence of fever was obtained by telephone on the third day after vaccination. The relative risk for fever in relation to the type of breastfeeding was estimated in multivariate analyses that adjusted for vaccine dose, maternal education and smoking, and number of other children in the household.

Results: A total of 460 infants were recruited, and information on the outcome was obtained for 450 (98%). Fever was reported for 30 (25%), 48 (31%), and 94 (53%) of the infants who were being exclusively breastfed, partially breastfed, or not breastfed at all, respectively (P < .01). The relative risk for fever among infants who were exclusively and partially breastfed was 0.46 (95% confidence interval: 0.33-0.66) and 0.58 (95% confidence interval: 0.44-0.77), respectively. The protection conferred by breastfeeding persisted even when considering the role of several potential confounders.

Conclusions: In this study, breastfeeding was associated with a decreased incidence of fever after immunizations.