Time of day may make flu shot more effective

Flu shots may be more effective when people get them in the morning than in the afternoon, a new study suggests.

Larger increase in antibodies

British researchers assessed 276 people 65 and older who received vaccinations against three different flu strains between 2011 and 2013. The patients received the vaccines either between 9 a.m. and 11 a.m., or 3 p.m. and 5 p.m.

People in the morning group had a much larger increase in antibodies against two of the flu strains one month after vaccination, the researchers found. However, with the third flu strain, there was no significant difference between the morning and afternoon groups.

Read: Winter is on its way – and so is the dreaded flu

"We know that there are fluctuations in immune responses throughout the day and wanted to examine whether this would extend to the antibody response to vaccination," said lead investigator Anna Phillips.

Improving vaccination strategies

She's with the University of Birmingham's School of Sport, Exercise and Rehabilitation Sciences.

"Being able to see that morning vaccinations yield a more efficient response will not only help in strategies for flu vaccination, but might provide clues to improve vaccination strategies more generally," Phillips said in a university news release.

Read: Seasonal flu vaccine even less effective than thought    

According to study co-author Janet Lord, "A significant amount of resource is used to try and prevent flu infection each year, particularly in older adults, but less than half make enough antibody to be fully protected."

Lord, a professor at the university's Institute of Inflammation and Ageing, said, "Our results suggest that by shifting the time of those vaccinations to the morning we can improve their efficiency with no extra cost to the health service."

The researchers said they plan to conduct a larger study on the timing of flu vaccinations to test their hypothesis. And they will also examine if morning vaccinations boost the effectiveness of the pneumococcal vaccine, which protects against pneumonia.

The study was published online in the journal Vaccine.

Read more:

Symptoms of flu

Diagnosing flu

Preventing flu

Image: Syringe from iStock

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