(Reuters) - Two-month-old babies who receive immunizations in the afternoon sleep better afterward than children who have their shots in the morning, according to a new study.

The results suggest a potential method for helping babies sleep through the occasional discomfort that accompanies vaccination, rather than taking a fever reducer as has often been recommended.

Sleep is important after getting shots, said lead author Linda Franck, because sleep is a sign of a vaccine response, and it's important to maximizing that response.

Acetaminophen, which goes by the brand name Tylenol, is commonly given to babies in advance of vaccinations to reduce any increase in temperature and to make them more comfortable.

But Franck's group reports in the journal Pediatrics that the drug did not appear to help extend sleep.

Franck and her colleagues at the University of California, San Francisco, had set out to test how well acetaminophen helps babies sleep after immunizations by randomly assigning children to either receive the fever-reducer before getting shots or not receive the medication.

The 70 two-month-olds in the study got a number of immunizations, including pneumococcal, diphtheria-tetanus-pertussis (DPT), Haemophilus influenzae type b, poliovirus and hepatitis B vaccines.

The vaccines are part of the Centers for Disease Control and Prevention's recommendations for routine immunizations.

Though 25 of the babies received a dose of acetaminophen before the shots, most of the babies in the study ended up being given acetaminophen at the time of the shots or afterwards to reduce any fever or discomfort.

All of them wore an ankle monitor that measured the amount of sleep before and after the vaccinations.

Most of the babies slept longer in the 24 hours after the vaccinations than in the 24 hours preceding the shots -- a total of 13 hours of sleep compared to fewer than 12 hours previously.

Those babies who received the shots after 1:30 in the afternoon were more likely to have a larger increase in sleep than babies whose appointments were earlier than 1:30 PM.

Infants who had their vaccinations in the afternoon slept an hour and a half longer, on average, than the day before, while infants who were seen in the morning slept only a half hour longer than the preceding day.

The number of doses of acetaminophen that the children received had no influence on the amount of sleep they got.

EARLIER STUDY QUESTIONED ACETAMINOPHEN

Dr. Jason Homme, a pediatrician at the Mayo Clinic in Rochester, Minnesota, said the results provide another reason to pause before using acetaminophen preventively for vaccinations.

Homme, who was not involved in this study, noted a study from 2009 that found that acetaminophen appeared to reduce the immune response to vaccines (see Reuters report of October 16, 2009).

That has caused some of us to reconsider giving (acetaminophen) in a preventative manner, said Homme.

Homme said that the importance of sleep regarding children's immune response to vaccines has not been fully worked out.

A study in adults found that they had a stronger immune response to vaccines if they were not sleep-deprived before or after the vaccinations.

Franck said she'd like to confirm her findings with another study, and if they hold up, it might make sense to schedule appointments for children's two-month vaccines in the afternoon.

It seems like a fairly easy thing to schedule that baby's first immunization in the afternoon so they spend less time in the day in discomfort and hopefully sleep it off and sleep longer, she said.

Franck said that making immunizations as pleasant an experience as possible for babies and their parents will encourage moms and dads to stick to the vaccine recommendations from the Centers for Disease Control and Prevention.

Homme agreed that it's important to make appointments as simple as possible for parents to get to, and there's no reason yet to postpone or avoid shots given in the morning.

SOURCE: bit.ly/uTdpYu, Pediatrics, November 28, 2011.

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