Impact of Vaccination Time on Anti-SARS-CoV-2 Antibody Levels in Adults: A Quasi-experimental Study.

BACKGROUND AND AIM

Vaccination time may provide an opportunity to advance immunogenicity in terms of the immune system's circadian nature. This analytical study was planned to determine the impact of forenoon and afternoon administration of the COVID-19 vaccine to adults on the magnitude of antibody response.

METHOD

A total of 33 healthy adults with no history of COVID-19 infection or any other disease participated in the study. They were allotted a forenoon (900-1200 hours) or afternoon (1200-500 hours) slot for vaccination. They were categorized as a forenoon or afternoon group, with 16 subjects in the forenoon and 17 in the afternoon group. With the consent of the participants, a blood sample was collected before vaccination, 30 days after the first and 30 days after the second dose of vaccination from all the subjects. The antibody titer response was measured using a commercial semi-quantitative assay, SARS-CoV-2 IgG II.

RESULTS

The baseline antibody titer against COVID-19 was 51.41 ± 22.22 AU/mL and 53.21 ± 15.67 AU/mL in the forenoon and afternoon groups, respectively, which increased to 15773.00 ± 3231.41 AU/mL and 12970.82 ± 7608.00 AU/mL after 30 days of the first dose of the COVID-19 vaccine in the forenoon and afternoon groups, respectively. This further increased to 37007.00 ± 1697.75 AU/mL and 38012.00 ± 14001.16 AU/mL after 30 days of the second dose of the COVID-19 vaccine in the forenoon and afternoon groups, respectively. There was no difference in antibody response in subjects with forenoon and afternoon vaccinations. There was no significant difference in antibody titer in males vs. females. The study reported that antibody titers decreased with increasing age and BMI of participants.

CONCLUSION

The time of the day of vaccination does not impact the immune response to COVID-19, but age and BMI are important factors to consider during vaccination against SARS-CoV-2 in the adult population.