The positive conversion rate and antibody level of COVID-19 serum IgG after second doses of 28d vaccination;The positive conversion rate and antibody level of 28d IgA antibody in nasopharyngeal swabs after second doses of vaccination;Levels of novel coronavirus spiking protein specific cellular immune response in whole blood at 28 days after inoculation of the second dose of vaccine (positive rate and relative level of IFN-? secreted after PBMC-stimulated culture);

The positive conversion rate and antibody level of COVID-19 serum IgG after second doses of 28d vaccination;The positive conversion rate and antibody level of 28d IgA antibody in nasopharyngeal swabs after second doses of vaccination;Levels of novel coronavirus spiking protein specific cellular immune response in whole blood at 28 days after inoculation of the second dose of vaccine (positive rate and relative level of IFN-? secreted after PBMC-stimulated culture);