Clinical

Breast-fed babies less feverish after immunization

Last Updated: 2010-05-19 19:56:11 -0400 (Reuters Health)

By Anne Harding

NEW YORK (Reuters Health) - Breastfeeding may protect babies from post-vaccine fevers, according to a new study published online May 17th in Pediatrics.

It's not uncommon for an infant's temperature to climb soon after immunization, Dr. Alfredo Pisacane of Universita Federico II in Napoli, Italy, and his colleagues note. While the elevations are usually mild, in 1% to 2% of cases the infants can have high fevers, which can be stressful for them (and their families).

Because breast- and bottle-fed babies are known to respond differently to vaccines and to illness, the authors investigated whether breastfeeding might protect against post-vaccine fever by having 450 mothers track of their infant's temperature for a few days after immunization.

When the babies received the first or second set of polyvalent vaccines (against diphtheria, tetanus, pertussis, hepatitis B, polio, Haemophilus influenzae type b, and pneumococcal infection), the mothers recorded the infant's rectal temperature that evening and daily for three more days.

One hundred twenty infants were being exclusively breastfed, 154 were partially breastfed, and 176 were bottle-fed. Babies receiving the vaccine for the first time were about three months old, on average. Those having their second set of shots were about six months old.

One-quarter of the exclusively breastfed babies, 31% of the partially breastfed babies, and 53% of the bottle-fed babies developed fevers of at least 38 degrees C (100.4 degrees F), the researchers found.

For 90% of the entire group, fever developed in the first day after immunization; three-quarters had fevers lasting just one day. Just eight of the infants - four partially breastfed, and four not breastfed - had fevers above 39 degrees C (just above 102 degrees F).

The apparent protective effect of breastfeeding remained after adjustment for factors like mother's education and the number of other children in the home.

Speculating about possible explanations for their findings, the authors note that breast milk could reduce the production of inflammation-promoting proteins released after immunization, and it could also comfort feverish children and encourage them to eat. The researchers point out that bottle-fed babies have been reported to consume fewer calories after immunization than breastfed babies do.

"When infants are sick and after a vaccination shot, they need not only water, food and a calm environment, but also to be protected," Dr. Pisacane told Reuters Health. "They need the warm body of their mothers. Breastfeeding provides all what an infant does need during illness."

http://pediatrics.aappublications.org/cgi/content/abstract/peds.2009-1911v1

Pediatrics 2010.