Breast-Feeding Linked to Lower Incidence of Fever After Immunizations

News Author: Laurie Barclay, MD
CME Author: Charles P. Vega, MD

May 19, 2010 — Breast-feeding is linked to a lower incidence of fever after immunizations, according to the results of a prospective cohort study reported online May 17 in Pediatrics.

"Immune response to some vaccines is different among breastfed infants compared with those who are not breastfed," write Alfredo Pisacane, MD, from Università Federico II in Napoli, Italy, and colleagues. "The objective of this study was to evaluate the effects of breastfeeding on the risk for fever after routine immunizations."

At a pediatric vaccination center in Naples, Italy, mothers of infants scheduled for routine vaccinations were told how to measure and record infant temperature on the evening that the immunization was administered and for the next 3 days. On the third day after vaccination, mothers were phoned to determine the incidence of fever. After adjustment for vaccine dose, maternal educational level and smoking status, and number of other children in the household, multivariate analyses allowed estimation of the relative risk for fever in relationship to the type of breast-feeding.

Of 460 infants recruited, outcome data were available for 450 (98%). Fever was reported in 30 (25%) of exclusively breast-fed infants, in 48 (31%) of partially breast-fed infants, and in 94 (53%) of infants who were not breast-fed at all (P < .01).
Among infants who were exclusively breast-fed, the relative risk for fever was 0.46 (95% confidence interval [CI], 0.33 - 0.66), and it was 0.58 (95% CI, 0.44 - 0.77) among partially breast-fed infants.

"The protection conferred by breastfeeding persisted even when considering the role of several potential confounders," the study authors write. "In this study, breastfeeding was associated with a decreased incidence of fever after immunizations."

Limitations of this study include body temperatures taken by the mothers rather than by health professionals and the possibility that fever after immunization could be an infective episode.

"Breastfeeding seems to be associated with a reduced risk for fever after immunization, but additional, well organized studies are needed," the study authors conclude. "The design of such studies should include more objective research methods, such as measurements taken by health care professionals at the same time of the day or night, and should evaluate the role of mild intercurrent infections by medical monitoring."

The study authors have disclosed no relevant financial relationships.

Pediatrics. Published online May 17, 2010.

Clinical Context

Breast-feeding can strengthen infants' immune systems, among other salutary effects. A previous study by Pabst and colleagues examined whether breast-fed infants experienced a more robust immune response to the conjugate H influenzae type b vaccine.
This research, which was published in the August 4, 1990, issue of The Lancet, did not find a difference in the immune response between breast-fed and formula-fed children at ages 2, 4, and 6 months. However, at ages 7 months and 12 months, the antibody levels against H influenzae were significantly higher among breast-fed vs formula-fed children.

Breast milk and the act of breast-feeding itself have properties that might reduce fever, particularly after vaccinations. The current study examines this hypothesis.