Senior living communities promoting influenza vaccination among staff members and residents may wish to add a time of day to the recommendation. Most flu vaccinations are more effective when administered in the morning, according to research published online April 26 by the journal Vaccine.

Investigators from the University of Birmingham in the United Kingdom reached their conclusion after analyzing flu shot administration in 24 general medical practices between 2011 and 2013. During that time, 276 adults aged more than 65 years were vaccinated against three flu strains, either in the morning (9 to 11 a.m.) or in the afternoon (3 to 5 p.m.).

They found that, in two of the three given flu strains, those who had been vaccinated in the morning saw a significantly larger increase in antibody concentration one month following vaccination, compared with those who had been vaccinated in the afternoon. In the third flu strain, no significant difference existed between morning and afternoon vaccination.

“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 Anna Phillips, Ph.D., the study’s principal investigator, who is affiliated with the university’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.”

Indeed, the team now plans to investigate whether the morning vaccination strategy would work with pneumonia vaccination, or for older adults who have diabetes, liver and kidney disease — conditions that impair immunity.

Vaccination effectiveness has special significance in senior living. Among United States healthcare workers, flu vaccination is lowest among those working in assisted living communities, nursing homes, home health and other long-term care settings, which puts residents at risk of getting the flu and becoming seriously ill, according to the Centers for Disease Control and Prevention. People aged 65 or more years are at greater risk of serious complications from the flu, including death, compared with young, healthy adults, because human immune defenses weaken with age.

Speaking at the recent Association of Health Care Journalists annual meeting, Ronan Factora, M.D., a geriatrician and co-director of the Cleveland Clinic’s Aging Brain Clinic, said that “vaccinations are very useful” in preventing illnesses, such as the flu, that could deprive older adults of function.