Time of day might not matter for COVID-19 vaccination

Research Press Release | October 12, 2022

A study in Japan finds antibody response to the Moderna COVID-19 mRNA vaccine does not vary depending on the time of day when the dose was received.

Ed Us/Unsplash

Many physiological and behavioral functions including the immune system exhibit circadian rhythms. Several studies have investigated if the immune response to COVID-19 vaccines varies depending on the time of day when the dose was received, but results were dependent on type of vaccine, participants’ age and sex.  Now, a study conducted by scientists at Hokkaido University and colleagues in Japan has found no association between antibody response to COVID-19 vaccine and time of day of vaccination. They do add to the body of literature that could ultimately guide vaccination optimization. The findings were published in the Journal of Biological Rhythms.

A video presentation posted to the Journal of Biological Rhythms‘s YouTube channel

The researchers recruited their study participants from Hokkaido University employees and students who received their first dose of the mRNA-1273 (Moderna) vaccine two to four weeks earlier. Those who had been previously infected with COVID-19 were excluded. The study group did not include shift workers, a crucial difference between this and some previous studies on healthcare workers.

The team collected demographic data on the final group of 332 Japanese participants and took blood samples to measure antibody titers against SARS-CoV-2. They then conducted statistical analyses to find out if there were associations between the time of day when the participants received their vaccine dose, any of the demographic characteristics, and the immune response.

The association between antibody titers and age (a) and antibody titers and time of day of vaccination (b), show that the time of has no effect on antibody titers, although there are some significant differences (asterisks and dagger) between age groups (Yujiro Yamanaka, et al. Journal of Biological Rhythms. September 26, 2022).

“Our analyses revealed no significant association between the time of day of vaccination and the SARS-CoV-2 antibody concentration, but we did find that antibody titers decreased in participants aged 50 to 64, which is consistent with previous studies,” says Hokkaido University physiologist Dr. Yujiro Yamanaka, who specializes in studying chronobiology.

Conflicting results between studies could be explained by various factors, including differences in sex, age, physical activity, and natural immune system, the type of vaccine received, number of days after vaccination, and differences in vaccine dose. Scientists also need to more fully understand whether other factors like race play a role.

“The limitations reduce our ability to conclusively rule out the possibility that circadian rhythms influence antibody response to vaccination,” says Yamanaka. “Larger randomized studies are needed to more conclusively guide vaccination strategies regarding a time-of-day variable.”

Yujiro Yamanaka, first and corresponding author of the paper (Photo: Yujiro Yamanaka).

Original Article:

Yujiro Yamanaka, et al. Time of Day of Vaccination Does Not Associate With SARS–CoV–2 Antibody Titer Following First Dose of mRNA COVID–19 Vaccine. Journal of Biological Rhythms. September 26, 2022.

DOI: 10.1177/0748730422112466


This work was supported by the Japan Agency for Medical Research and Development (AMED; JP20ek0210154).


Associate Professor Yujiro Yamanaka

Laboratory of Life and Health Sciences

Graduate School of Education and Faculty of Education

Hokkaido University

Tel: +81-11-706-3077

Email: y-yu2ro[at]edu.hokudai.ac.jp

Sohail Keegan Pinto (International Public Relations Specialist)

Public Relations Division

Hokkaido University

Tel: +81-11-706-2186

Email: en-press[at]general.hokudai.ac.jp