Dynamic observation of SARS‐CoV‐2 IgM, IgG, and neutralizing antibodies in the development of population immunity through COVID‐19 vaccination

BACKGROUND: Currently, mass vaccine inoculation against coronavirus disease‐2019 (COVID‐19) has been being implemented globally. Rapid and the large‐scale detection of serum neutralizing antibodies (NAbs) laid a foundation for assessing the immune response against SARS‐CoV‐2 infection and vaccine. Additional assessments include the duration of antibodies and the optimal time for a heightened immune response. METHODS: The performance of five surrogate NAbs—three chemiluminescent immunoassay (CLIA) and two enzyme‐linked immunosorbent assays (ELISAs)—and specific IgM and IgG assays were compared using COVID‐19‐vaccinated serum (n = 164). Conventional virus neutralization test (cVNT) was used as a criterion and the diagnostic agreement and correlation of the five assays were evaluated. We studied the antibody responses after the two‐dose vaccine in volunteers up to 6 months. RESULTS: The sensitivity and specificity of five surrogate NAb assays ranged from 84% to 100%. Our cVNT results indicated great consistency with the surrogate assays. At 28 days after primary vaccination, the seropositivities of the NAbs, IgG, and IgM were 6%, 4%, and 13%, respectively. After the booster dose, seropositivities reached 14%, 65%, and 97%, respectively. Six months after receipt of the second dose, the NAb positive rate was eventually maintained at 66%. In all COVID‐19 convalescents, patients were detected with 100% NAb sat three months after discharge. CONCLUSION: COVID‐19 vaccine induced a humoral immune response lasting at least six months. Rapid serological detection was used as a proxy for identifying changes in immunity levels and as a guide to whether an individual may require a booster vaccination.