Booking a Covid booster jab in the afternoon could provide a higher number of antibodies, a new study suggests, although researchers insist receiving a vaccination at any hour remains the best method of protection against infection.

Scientists at Massachusetts General Hospital in the US found that the time of day a vaccine is administered can affect the number of antibodies produced, because of a bodily function – which affects the immune system’s reaction to infectious diseases – that reacts differently throughout a 24-hour cycle.

The cycle, known as a circadian rhythm, can affect how seriously some people suffer from diseases and how effective medical treatments are.

The team, which assessed the antibody levels of 2,190 British healthcare workers who had received the Pfizer or AstraZeneca vaccine, found that people who received a vaccine later in the day had higher antibody levels, but said their research is not yet complete enough to recommend people to schedule their vaccination appointments at certain times.

Time of day and immune response

Professor Elizabeth Klerman, a neurophysiology researcher at the hospital, who authored the study, said: “Our observational study provides proof of concept that time of day affects immune response to SARS-CoV-2 vaccination, findings that may be relevant for optimising the vaccine’s efficacy.”

“We need to replicate our findings and develop a better understanding of the underlying physiology of SARS-CoV-2 and the body’s response to vaccination before we can recommend that people who want an extra boost from the vaccine, such as older individuals or those who are immunocompromised, schedule their vaccine for the afternoon.

“This research is the first step in demonstrating the importance of time-of-day response to SARS-CoV-2 vaccine.”