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.
Timing of Vaccinations
In the study, researchers compared sleep duration and body temperature in 70 infants about 2 months old in the 24 hours before and after their first immunization.
Researchers say there are conflicting recommendations about whether parents should give their infants acetaminophen before and after receiving immunizations to ease discomfort or help them sleep.
Overall, the study showed infants slept for an average of 69 minutes longer in the 24 hours following immunization than in the 24-hour period before immunization.
Researchers found that on average all the infants slept longer after immunization. Infants who got their immunizations after 1:30 p.m. and those who had elevated body temperatures in response to the vaccines slept the longest over the next 24 hours.
Researchers found acetaminophen was not a significant factor in sleep duration after accounting for other factors, such as fever or discomfort.