Vaccination Effectiveness Depends on the Time of Day It's Given

Flu vaccinations appear to be more effective when given in the morning as opposed to the afternoon.

The Centers for Disease Control and Prevention (CDC) recommends that everyone — unless otherwise specified – above the age of 6 months should get the flu vaccine. Although the primary goal is to encourage as many people as possible to get vaccinated, it turns out that the time of day the vaccine is received influences immune responses.

“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,” principal investigator Anna Phillips, PhD, MSc, BSc (Hons), from the School of Sport, Exercise and Rehabilitation, said in a news release.

In the first large-scale trial assessing vaccination times, researchers from the University of Birmingham in England analyzed 276 adults over the age of 65 between 2011 and 2013. The participants were healthy at the time of the study and did not have immune system disorders. They were vaccinated against three strains of influenza either in the morning (9 a.m. to 11 a.m.) or afternoon (3 p.m. to 5 p.m.).

• Related: Flu Vaccination in Pregnant Women May Be the Difference Between Life and Death

The vaccines for H1N1 A-strain and B-strain proved to work significantly better in those who received them in the morning hours. A significantly larger amount of antibody concentration was observed one month after the vaccinations in these cases. The H3N2 A-strain vaccine, however, did not show a difference between the groups, as detailed in the journal Vaccine.

“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 continued.

Last year it was uncovered that the amount of older adults getting flu vaccinations was not meeting CDC recommendations. With recent research confirming that the vaccines do in fact protect this population, these findings can help healthcare providers distribute them better.

“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,” summed up co-investigator Janet Lord, BSc, PhD, FMedSci.

The researchers plan to further investigate flu vaccines to see if the morning benefits expand to a wider age range. In addition, they will test if results also apply to the pneumococcal vaccine against pneumonia.

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