Breastfeeding may give baby a boost when it comes to routine vaccinations, according to a new study from Italy that suggests breastfed infants are less likely to develop a fever following routine immunizations. Published online May 17, 2010, in the journal Pediatrics, the study tracked post-vaccination temperature readings in a group of 450 infants—from the evening of a routine vaccination and for three days afterward. During this time period, fever was reported in 25 percent of exclusively breastfed infants, 31 percent of partially breastfed babies, and 53 percent of infants exclusively fed formula. Even after taking other factors into account, including exposure to cigarette smoke, moms' levels of education, the number of other children in the household, and vaccine dose, researchers still found that breasted babies were at lower risk.
It's unclear from this study exactly how breast milk wards off fever, but researchers think anti-inflammatory properties of human milk or even the act of nursing itself could be factors.
"Human milk is rich in anti-inflammatory substances and this could be a reason for ... reduced incidence of fever. But fever could also be due to [poor feeding], which is common when children are sick. As breastfed infants are less likely to have poor feeding, probably because breastfeeding is source of comfort during illness, another reason why fever is less likely among breastfed infants is that they consume more food when they are sick," the research team concludes.
Because fever is a common side effect of most routine childhood immunizations, make sure to discuss with your child's pediatrician what to do in case of fever—including when to call the doctor or bring Baby in. Your pediatrician can also provide detailed information about the specific shots your child will receive, including a list of possible reactions. Other common vaccine side effects include redness or soreness at the injection site.