Comparison of the immunogenicity of BNT162b2 and CoronaVac COVID‐19 vaccines in Hong Kong

BACKGROUND AND OBJECTIVE: Few head‐to‐head evaluations of immune responses to different vaccines have been reported. METHODS: Surrogate virus neutralization test (sVNT) antibody levels of adults receiving either two doses of BNT162b2 (n = 366) or CoronaVac (n = 360) vaccines in Hong Kong were determined. An age‐matched subgroup (BNT162b2 [n = 49] vs. CoronaVac [n = 49]) was tested for plaque reduction neutralization (PRNT) and spike‐binding antibody and T‐cell reactivity in peripheral blood mononuclear cells. RESULTS: One month after the second dose of vaccine, BNT162b2 elicited significantly higher PRNT(50), PRNT(90), sVNT, spike receptor binding, spike N‐terminal domain binding, spike S2 domain binding, spike FcR binding and antibody avidity levels than CoronaVac. The geometric mean PRNT(50) titres in those vaccinated with BNT162b2 and CoronaVac vaccines were 251.6 and 69.45, while PRNT(90) titres were 98.91 and 16.57, respectively. All of those vaccinated with BNT162b2 and 45 (91.8%) of 49 vaccinated with CoronaVac achieved the 50% protection threshold for PRNT(90.) Allowing for an expected seven‐fold waning of antibody titres over 6 months for those receiving CoronaVac, only 16.3% would meet the 50% protection threshold versus 79.6% of BNT162b2 vaccinees. Age was negatively correlated with PRNT(90) antibody titres. Both vaccines induced SARS‐CoV‐2‐specific CD4(+) and CD8(+) T‐cell responses at 1 month post‐vaccination but CoronaVac elicited significantly higher structural protein‐specific CD4(+) and CD8(+) T‐cell responses. CONCLUSION: Vaccination with BNT162b2 induces stronger humoral responses than CoronaVac. CoronaVac induces higher CD4(+) and CD8(+) T‐cell responses to the structural protein than BNT162b2.