A comparative analysis of two COVID-19 vaccines found that the difference in concentrations of neutralising antibodies could interpret substantial differences in vaccine effectiveness, as issued in The Lancet-Microbe journal. Hence, neutralising antibody titres have been suggested to be associated with the protection of vaccines against COVID-19. This conclusion was based on information on SARS-CoV-2 vaccine immunogenicity in 1442 healthcare workers who were either given BNT162b2 or inactivated virus vaccine.

Blood samples were collected following their informed consent at different time points, i.e. prior to the first dose, prior to the second dose and 21 to 35 days following the second dose. Samples were tested for antibodies to SARS-CoV-2, analysis of ELISA-positive samples was done for neutralising antibodies, and then a plaque reduction neutralisation test (PRNT) was performed to calculate the titer of neutralising antibody with live COVID-19 virus.

Primary laboratory testing outcomes on 93 individuals with complete data on antibody concentrations at specified time points were presented. Out of these, 63 individuals (55.6% men, median age of 37 years) were fully vaccinated with the BNT162b2 vaccine and 30 individuals (23·3% women, median age of 47 years) with both doses of the inactivated vaccine.

Compared to participants with inactivated vaccine, the antibody concentrations considerably increased in those with BNT162b2 vaccine following the first dose and then again surged after the second dose. In both vaccine groups (a subset of 12 participants), the geometric mean PRNT₅₀ titre and PRNT₉₀ titre varied as shown in Table 1:

Other possible correlates of protection (T cells or antibody-dependent cellular cytotoxicity antibody) has not been included in this study. Future studies could explore the substitute approaches to augment antibody concentrations and clinical protection in receivers of inactivated vaccines, including administration of booster doses, the study authors noted.