Serum anti-SARS-CoV-2 IgA, IgM and IgG among confirmed COVID-19 cases at different stages and inactivated COVID-19 vaccine recipients after inoculation: a comparative analysis

ObjectiveTo examine time-dependent variations in serum antibodies of severe acute respiratory disease coronavirus 2 (SARS-CoV-2) among confirmed coronavirus disease 2019 (COVID-19) cases at different stages and inactivated COVID-19 vaccine recipients after inoculation. MethodsThe study was conducted in a city of Henan province. Totally 86 serum samples were collected from 43 confirmed COVID-19 cases at acute stage (1th – 23rd day of onset) and recovery state (25th – 58th day of onset) during January 2020 – October 2021; other 184 serum samples from 46 healthy recipients of inactivated COVID-19 vaccine at 4/8/12/31 weeks after inoculations and 50 serum samples from 50 residents without confirmed SARS-CoV-2 infections were also collected during March – October 2021. Anti-SARS-CoV-2 immunoglobulin A/G/M (IgA/G/M) were detected with magnetic particle chemiluminescence method and enzyme-linked immunosorbent assay for all the serum samples. The levels of the serum antibodies among the three groups′ participants wer