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."
She added that Covid vaccination remains “the most critical step in preventing” infection and severe illness, “regardless of the time of day”.
Antibodies were also greater in women and young people, as well as those who received the Pfizer vaccine, which challenges earlier studies that concluded the flu vaccine to be more effective for older men when administered in the morning.
During the study, published in The Journal of Biological Rhythms on December 4, a model was developed to see whether the health workers’ gender or age affected how many antibodies they had after getting jabbed.
Scientists measured antibody levels by using blood samples that had been collected two to 10 weeks after receiving a first Covid vaccine dose.
Importance of time of day
It also examined whether the type of vaccine or the time of day when it was administered had any impact on the body’s Covid defences.
Prof Klerman said: "If preliminary data show a difference in efficacy and adverse effects from a drug or vaccine based on time of day, it would behove drug companies to administer the drug at the optimal time, which would reduce the number of participants needed to get a statistically significant difference between drug and placebo."
The team said more research is required into the timing of vaccines, as the study lacked data on the medical history of participants and their sleep and work patterns, each of which could influence how well people respond to vaccination.
It also did not include children, older people or those who are immunosuppressed.
They are now analysing data from patients at Mass General Brigham facilities in the US to assess whether vaccine timings could also impact how likely people are to experience side effects.
Prof Klerman said: “If antibody levels are higher when people receive the vaccine in the afternoon, we may see that side effects are also greater.”
The Government has rushed to extend the booster programme in the weeks running up to Christmas, amid concerns over the omicron variant, with 30-year-olds set to be offered their jabs from Monday.
Data shows that a third jab provides up to 75 per cent protection against infection from omicron, as well as decreasing the chances of severe illness if infected.