Abstract
Assessing the duration of neutralizing antibodies (nAbs) following SARS-CoV-2 infection or vaccination is critical to evaluate the protective immunity and formulate public health strategies. In this study, SARS-CoV-2 Ab ELISA (enzyme-linked immunosorbent assay), chemiluminescent microparticle immunoassay (CMIA), as well as pseudovirus neutralization test (PVNT) were performed in two cohorts, convalescent patients (CP) from coronavirus disease 2019 (COVID-19) and BBIBP-CorV vaccinated population. It was found that nAbs and binding antibodies emerged at 14 days post the 1st dose of vaccination, reached peaks at 28 days after 2nd dose vaccination and then gradually declined over time. CP-6M (convalescent patients up to 6 months) from COVID-19 presented stronger nAbs or binding antibodies responses than vaccinees 90 days or 180 days after 2nd dose vaccination. CMIA or SARS-CoV-2 Ab ELISA correlated well with PVNT with high consistency in the two cohorts. It shown that nAbs and binding antibodies can keep 6 months both in CP and vaccinees. Most importantly, our data show the application of using CMIA and SARS-CoV-2 Ab ELISA as rapid screening tests for nAb titer and could be used as alternative strategies for quickly evaluating SARS-CoV-2 nAbs responses in vaccine research.
Highlights
In cohort 1, 40 individuals who had recovered from COVID-19 approximately six months (158–198 days) were recruited (Figure 1)
PVNT50, SARS-CoV-2 Ab enzyme-linked immunosorbent assays (ELISA) and chemiluminescent microparticle immunoassay (CMIA) were 20, 0.19 and 1.00 separately, and neutralizing antibodies (nAbs) responses showed no difference among subgroups divided by gender, age, and disease severity (Figure 2)
We found that the results of CMIA or SARS-CoV-2 Ab ELISA correlated well with pseudovirus neutralization test (PVNT) and had a high consistency with the PVNT, no matter in the population of convalescents, vaccinated or two cohorts combined
Summary
As of 14 January 2022, 318,648,834 confirmed cases of COVID-19, including. A total of 9,283,076,642 vaccine doses have been administered. Inactivated vaccine BBIBP-CorV (China Sinopharm Bio-Beijing Company) was the first vaccine approved for emergency use by WHO on 7 May 2021and is widely vaccinated in China. All BBIBP-CorV-vaccinated individuals seroconverted successfully by 42 days after the 1st dose vaccination [1]. A phase 3 clinical trial confirmed the protection of the BBIBP-CorV vaccine with an efficacy of 78.1% reduction of asymptomatic illness [2]
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