Nov. 29, 2011 -- Scheduling infant immunizations in the afternoon may lead to an increase in the infant's sleep over the next 24 hours.

A new study shows that infants who received their vaccinations after 1:30 p.m. were more likely to sleep longer and have a small increase in body temperature in the 24 hours following vaccination.

A small rise in body temperature is an expected reaction in infants getting an immunization, and can be a sign of a good immune response.

Sleep also plays an important role in the immune response. Previous research in adults has shown that lack of sleep before or after getting a shot may lead to a weaker immune response to the vaccine.

"Given the importance of sleep for a healthy immune response, our findings suggest that the time of day of vaccine administration and sleep duration after immunization are important to consider," researcher Linda Frank, RN, PhD, of the University of California, San Francisco, writes in Pediatrics.

If the relationship between timing of immunizations and immune response are confirmed by further studies, researchers say afternoon immunizations should be recommended for infants.