When is the best time to get a COVID vax?
Getting a coronavirus vaccine or booster shot in the afternoon might trigger higher levels of antibodies compared with getting the shot in the morning, a study out of Massachusetts General Hospital suggests.
“Our observational study provides proof of concept that time of day affects immune response to SARSCoV-2 vaccination, findings that may be relevant for optimizing the vaccine’s efficacy,” said co-senior author Dr. Elizabeth Klerman, an investigator in the division of neurophysiology at Massachusetts General Hospital.
Klerman and her colleagues looked at antibody levels after vaccination among 2,190 health care workers in the U.K. and created a model to investigate the effect on antibody levels based on time of day, age, sex and other factors.
The health care workers had received either the Pfizer vaccine or the AstraZeneca vaccine.
Antibody responses were higher in general for everyone who was vaccinated later in the day — after 11 a.m. — compared with people who got the shot earlier in the morning.
The antibody responses were also higher in those who received the Pfizer vaccine, in women, and in younger people, the study shows.
“This research is the first step in demonstrating the importance of time-of-day response to SARS-CoV-2 vaccine,” Klerman said.
She emphasized that more studies must be done before a recommendation to get vaccinated in the afternoon is made, and that simply getting vaccinated in the first place, regardless of timing, is most important right now.
“If you can only get vaccinated in the morning, absolutely get vaccinated in the morning,” Klerman told the Herald.
She said many other medicines and treatments have been shown to have different effects when administered during different times of day. For example, cholesterol medicines are most effective when taken at night.
A limitation of this study was the lack of data on participants’ medical and medication history, their sleep and shift-work patterns, which can also influence vaccine responses.
The data also highlights the importance of recording the time of vaccination in clinical and research studies. Klerman said she’s currently working with drug companies who make coronavirus vaccines to learn more about this.
Klerman and her colleagues are currently analyzing data on vaccine side effects from people vaccinated at Mass General Brigham facilities. “If antibody levels are higher when people receive the vaccine in the afternoon, we may see that side effects are also greater,” Klerman said.