Comparative analysis of humoral immunity kinetics following three COVID-19 vaccines in a multi-ethnic cohort of medical students and healthcare professionals across Malaysia.

The objective of our study was to evaluate the time-dependent humoral immunity kinetics among multi-ethnic population of medical students and healthcare professionals across Malaysia following two doses of Comirnaty, Vaxzevria, and CoronaVac vaccines. Prospective observational cohort research was carried out from September 2021-March 2023. 242 vaccine recipients have completed the follow-up. After second vaccination dosage, peripheral blood was drawn every four weeks from week 0-24. Anti-S IgG and percentage of neutralization were measured from each individual plasma sample. Recipients of Comirnaty and Vaxzevria vaccine, exhibited adequate anti-S IgG and neutralizing antibody till week 24. In compared to Comirnaty/Vaxzevria vaccine group, CoronaVac group showed significant decrease of antibody as early as week 12. The Comirnaty vaccine peaked anti-S IgG production at week 4, while the Vaxzevria and CoronaVac vaccines peaked at week 2. The Comirnaty vaccine (91.3%) showed strong Ig-RBD neutralizing antibody response even after week 24, which led to the slowest rate of antibody waning when compared to CoronaVac (13%), which never achieves high Ig-RBD neutralizing antibody. The percentage of inhibition of Ig-RBD binding on ACE receptor and anti-S IgG seroconversion were significantly higher in the Comirnaty vaccine. The antibody response of Comirnaty was lower in recipients with higher BMIs than in those with normal or low BMIs. Higher BMI, however, was associated with more robust humoral immune responses to Vaxzevria vaccine. Following immunisation, the Chinese and Indian populations might exhibit a stronger humoral immune response than the Malay population.