SARS-CoV-2-specific serum IgG and mucosal IgA responses
Concentrations of anti-SARS-CoV-2 IgG and IgA antibodies were assessed before and after the boost. (Wild-type SARS-CoV-2 RBD-specific binding antibody responses. The level of saliva IgA at day 0 and 14 after boost was also measured to evaluate the mucosal immune response induced by different vaccines. An obvious increase in IgA response to spike at day 14 was observed in intramuscular Ad5-nCoV (2.68-fold, p<0.001), aerosolized Ad5-nCoV (2.59-fold, p<0.001) and ZF2001 (1.33-fold, p=0.0027) recipients compared with that in CoronaVac recipients (These data suggest that heterologous boosting with Ad5-nCoV via different routes can elicit significantly higher RBD-specific IgG levels than ZF2001 or CoronaVac, and the aerosolized Ad5-nCoV induced a distinct mucosal immune response.