ABSTRACT
Objective @#To investigate the serum levels of antibodies against SARS-CoV-2 after inoculation of an inactivated SARS-CoV-2 vaccine, so as to provide insights into the evaluation of the vaccine immunogenicity. @*Methods @#In this single-arm Objective performance criteria trial, residents aged 18 to 59 years and inoculated with an inactivated SARS-CoV-2 vaccine in Xihu District, Hangzhou City from October to December of 2020 were selected using a cluster sampling method. Blood samples were collected prior to inoculation, 14 and 28 days post-inoculation of the first dose, and 28 days post-inoculation of the second dose. Serum levels of anti-SARS-CoV-2 IgM and IgG antibodies were detected using the magnetic particle-based chemiluminescence immunoassay. The seroconversion of antibodies and dynamic changes of antibody levels were analyzed.@*Results @#Totally 310 participants were enrolled, including 133 subjects on day 14 post-inoculation of the first dose, 97 subjects on day 28 post-inoculation of the first dose and 254 subjects on day 28 post-inoculation of the second dose. The seroconversion rates of anti-SARS-CoV-2 IgG antibody were 6.02%, 28.87% and 98.43%, and the median IgG antibody levels were 1.76 ( interquartile range, 3.25 ), 5.69 ( 9.95 ) and 52.05 ( 47.60 ) AU/mL ( P<0.05 ), respectively, while the seroconversion rates of anti-SARS-CoV-2 IgM antibody were 9.02%, 11.34% and 12.99%, and the median IgG antibody levels were 1.89 ( 3.28 ), 2.06 ( 4.71 ) and 2.65 ( 4.01 ) AU/mL ( P>0.05 ), respectively. In addition, higher serum levels of anti-SARS-CoV-2 IgG and IgM antibodies were detected post-inoculation relative to pre-inoculation ( P<0.05 ), and higher serum IgG antibody levels were found in subjects aged 18 to 39 years than in those aged 40 to 59 years ( P<0.05 ). @*Conclusions @#Inoculation of two doses of the inactivated SARS-CoV-2 vaccine achieves a high immunogenicity among residents aged 18 to 59 years 28 days post-inoculation, and the anti-SARS-CoV-2 IgM antibody is detectable in some residents following inoculation of the first dose.
ABSTRACT
Objective:To detect the serum levels of SARS-CoV-2-specific IgM and IgG antibodies in patients infected with SARS-CoV-2 and recipients of inactivated vaccine in different periods for understanding their variation patterns in vivo. Methods:Chemiluminescence immunoassay was used to detect the levels of SARS-CoV-2-specific IgM and IgG antibodies in 144 serum samples of 44 COVID-19 patients, 381 serum samples of 118 asymptomatic infected cases and 398 serum samples of 273 inactivated vaccine recipients collected at different periods. The results were statistically analyzed together with basic characteristics and vaccination status.Results:The positive rates of IgM antibody in COVID-19 patients, asymptomatic infected cases and inactivated vaccine recipients were 52.27% (23/44), 23.73% (28/118) and 14.29% (39/273). The positive rate of IgM antibody was higher in COVID-19 patients than in asymptomatic infected cases and vaccine recipients (χ 2=12.106, P=0.001; χ 2=34.755, P<0.001). The positive rates of IgG antibody in the three populations were 100.00% (44/44), 97.46% (115/118) and 98.81% (166/168), and the differences were not statistically significant (χ 2=2.944, P=0.229). In COVID-19 patients, the concentration of IgM antibody in <40 years old group was lower than that in ≥40 years old group (Waldχ 2=6.609, P=0.010), and the concentration of IgG antibody in patients with vaccination was higher than that in patients without vaccination (Waldχ 2=12.402, P<0.001). In asymptomatic infected cases, the concentration of IgG antibody was higher in people with vaccination than in those without vaccination (Waldχ 2=4.530, P=0.033). In SARS-CoV-2 vaccine recipients, the concentration of IgG antibody in <40 years old group was higher than that in ≥40 years old group (Waldχ 2=9.565, P=0.002). Dynamic analysis of antibody levels showed that from week 1 to week 9, the concentrations of IgM and IgG antibodies in COVID-19 patients were higher than those in asymptomatic infected cases and vaccine recipients. Conclusions:The concentrations of IgM and IgG antibodies in COVID-19 patients were higher than those in asymptomatic infected cases and inactivated vaccine recipients. COVID-19 patients aged ≥40 years had higher level of IgM antibody. COVID-19 patients and asymptomatic infected cases who had received vaccination had higher concentration of IgG antibody. Inactivated vaccine showed good immunogenicity after whole course of immunization, and the IgG antibody level in <40 years old group was higher.