Flu vaccine taken in morning more effective: Study

Researchers from England say one was better off getting one's flu shot in the morning than in the afternoon.

''This is a free [course of action] that could seriously boost older adults' vaccination response with no adverse effects,'' reports quoted Dr Anna Phillips from the University of Birmingham as stating in an e-mail.

Vaccines work to stimulate the immune system to produce infection-fighting antibodies that could swing into action upon exposure to the actual disease. Given that the immune response varied through the course of the day, some researchers had suggested that vaccines might work better if they were given at some times of the day rather than at other times.

In a group of 276 older adults, Phillips's team assigned some to receive an influenza vaccine in the morning (9 am to 11 am) and the rest in the afternoon (3 pm to 5 pm).

A month later, the researchers analysed blood samples from each person to measure antibodies against the flu virus. Antibody levels were significantly higher in those subjects who had vaccinations in the morning, instead of in the afternoon, the authors reported in the journal Vaccine.

The response was found to be better in both women and men after the morning vaccination.

The researchers studied a variety of immune and hormone factors, they could not come with an explanation as to what they were seeing. ''We don't yet know exactly how this morning effect is working,'' Reuters reported Phillips as saying.

The study focused only on the anti-body levels, not on whether people actually got the flu later on.

Still, Phillips advises, ''Don't wait for the definitive trial to check that the increased levels of antibodies related to decreased disease risk. We know that's what antibodies do . . . so start this now.''

However, Dr Bruce Y Lee, director of operations research for Johns Hopkins Bloomberg School of Public Health's International Vaccine Access Center in Baltimore, Maryland, warned, ''We should be careful about jumping to conclusions from the study,'' Reuters Health Lee as stating in an email.