Mixing versus matching booster vaccines: A longitudinal humoral immune kinetics against Omicron in a Malaysian cohort.

OBJECTIVE

The objective of our study was to evaluate the longitudinal humoral immune response following booster regimens in Malaysia during the Omicron outbreak.

METHODS

In this prospective cohort study, 268 healthcare professionals and medical students in Malaysia were followed up for 24 weeks following homologous (mRNA-mRNA (mR-mR), viral vector-viral vector (VV-VV), inactivated virus-inactivated virus (IV-IV) and heterologous (inactivated virus-mRNA (IV-mR), viral vector-mRNA (VV-mR) booster vaccines. Of them, 190 recipients underwent longitudinal immunogenicity study. Anti-S IgG and anti-RBD response were assessed by ADVIA Centaur SARS-CoV-2 chemiluminescent immunoassay followed by surrogate virus neutralization test using Omicron-variant across all boosters.

RESULTS

Compared to homologous boosters, heterologous regimens, particularly the IV-mR booster, elicited significantly higher and sustained anti-S IgG and anti-RBD antibody (P<0.0001) responses. Over 24 weeks, the heterologous IV-mR booster had 100% seropositive anti-S IgG and anti-RBD antibodies, conversely, in the homologous (IV-IV) booster, the seropositivity of anti-S IgG and anti-RBD antibody reduced to 15.63% and 18.75% respectively. Omicron-virus neutralizing activity was observed as high as 95.92% (IV-mR) and 83.87% (VV-mR) following W24 of the heterologous booster, while virus neutralization was found as low as 9.38% in the IV-IV homologous booster. Age, gender, and ethnicity were not found as confounding factors for antibody kinetics following booster vaccine.

CONCLUSION

In conclusion, heterologous booster vaccines induced superior prolonged humoral-immune response against COVID-19 infection.