Morning jabs better for flu vaccination – Expert reaction

Influenza vaccinations are more effective in the morning, reports a new study.

The UK research, published in the journal Vaccine, compared the immune response of 276 older adults vaccinated in the morning  or afternoon, and found that morning-vaccinated people had more influenza-fighting antibodies when tested one month later

Read more about the study on

The Science Media Centre collected the following expert commentary on the report.

Dr Helen Petousis-Harris, Academic Head, Immunisation Research and Vaccinology, Immunisation Advisory Centre, comments:

“In light of what is known on this topic, these findings are not surprising and they are certainly exciting. It would be great if we could improve the performance of influenza vaccine in older people just by vaccinating in the morning.

“We have known for many years that the immune response can be altered, either positively or negatively, by a variety of stressors such as examinations, running marathons and also not getting enough sleep or sleeping at odd times. Many experiments have used influenza vaccine to measure the effect of these sorts of stressors on immunity.

“However, we do need exercise caution as while we know that a higher antibody response to flu vaccine is more likely to be protective we do not yet know if vaccinating in the morning will translate to better clinical protection against disease – those studies have yet to be done.

“I guess if you are over 65 and have the option of a morning appointment, why not take it. I cannot see a reason why not to.”

Our colleagues at the UK SMC collected the following commentary

Dr Ben Neuman, Lecturer in Virology, University of Reading, said:

“I think the most important message to take away from this study is that vaccinations work, no matter what time of day they are given.

“It takes around a month after vaccination for the body to make a mature antibody response.  In that month, there are millions of chance encounters between cells of the immune system and the vaccine, and then a period where many times as many cells randomly stitch and mutate bits of DNA in an attempt to build working antibodies.  The idea that a six-hour delay in the start of the month-long, mostly random process of making antibodies could make any meaningful difference to the outcome doesn’t make much sense to me.

“What I think happened is that, despite following what appeared to be a reasonable experimental design, there was enough of a difference between the people in the morning vaccine group and the afternoon vaccine group to skew the results.”

Dr Rachel Edgar, Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge, said:

“This robust study shows that our antibody responses to seasonal flu vaccines depend on the time of day at which they are given, and suggests vaccines may be more effective when administered in the morning, rather than afternoon. Further investigation is required to determine if morning vaccination strategies reduce the incidence of disease, and how vaccine efficacy is governed by our circadian (24h) rhythms.

“Individual cells in the body are able to keep track of time using their biological clocks, including immune cells that respond to infectious diseases. Currently we know very little about how our circadian clocks interact with viruses at the molecular level. The preliminary findings in this paper highlight the potential health and economic benefits we could glean from understanding the interaction between circadian rhythms and flu.”

Prof Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:

“We know that a variety of factors, such as diet, sleep and exercise seem to impact on your immunity, but the fact that the amount of antibody produced following influenza vaccination differed according to whether or not the people included in the study were immunised in the morning or in the afternoon was intriguing.

“But we have to remember – differences in antibody yield that are statistically significant might not be biologically significant, and that’s the key issue. We would need to see whether or not people vaccinated in the afternoon were more likely to become infected by the virus before we could say that timing of immunisation impacts on success.”

Dr Richard Pebody, head of flu surveillance for Public Health England, said:

“This is an interesting study and indicates more research is needed. Flu vaccine is the best protection we have against an unpredictable virus which can cause severe illness and deaths each year among at-risk groups, including older people, pregnant women and those with a health condition, even one that is well managed.”