Study Suggests Afternoon Immunizations May Be Best For Infants

Infants who receive vaccination shots in the afternoon tend to sleep better than those who are immunized at other times during the day, claims a study published in the December issue of the journal Pediatrics.

The study looked at 70 children who were approximately two months of age and receiving their first vaccines. It focused specifically on how long those infants slept and their body temperature in the 24 hour periods before and after receiving the immunization shot.

While all of the infants tended to sleep longer after the immunization than before it, those who received the shots after 1:30pm and those who had elevated body temperatures caused by the vaccines slept the longest during the next 24 hour period, WebMD’s Jennifer Warner said in an article published November 29 on

“Half of the parents were also instructed to give their infant a dose of acetaminophen (baby Tylenol) 30 minutes before the immunization and every four hours thereafter for a total of five doses,” Warner wrote, adding that that “there are conflicting recommendations about whether parents should give their infants acetaminophen before and after receiving immunizations to ease discomfort or help them sleep,” but that the new study found that “acetaminophen was not a significant factor in sleep duration after accounting for other factors, such as fever or discomfort.”

According to Denise Mann of USA Today HealthDay, lead author Linda Franck and colleagues also report that the change in sleep habits was also unrelated to the infant’s age or weight, but that more research was needed before they can make any concrete recommendations regarding the best time of day to have a child vaccinated.

“Based on what we currently know about sleep and the immune system, parents should try to help their babies to sleep well in the days before as well as after immunizations,” Franck, a pediatric nurse at the University of California, San Francisco, told Mann on Friday. “What we are learning about sleep and immune response to vaccines is just another reason for parents to learn how to help their baby sleep well.”

Dr. Carol Baker, a professor of pediatrics, molecular virology and microbiology at the Baylor College of Medicine, is quoted by USA Today as pointing out that the study was “small” and confined to a single medical center, and that a “huge study with multiple sites” would be required to confirm that the afternoon would be the best time to have a youngster immunized.

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