ArticleJournal of family medicine and primary care2025
A longitudinal study depicting persistence of COVID-19 antibodies after half a year using chemiluminescent microparticle immunoassay among healthcare workers and frontline workers in Mumbai, India's largest metropoli.
Article in Journal of family medicine and primary care, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
Introduction: Antibodies play a role in herd immunity, and studies estimate that COVID-19 antibody protection lasts approximately 1 to 4 months following COVID-19 vaccination and 6 to 8 months following infection. As healthcare workers and frontline workers were highly exposed to the infection, it is necessary to know if they have developed immunity against COVID-19. Aim: To estimate the seroprevalence of SARS-CoV-2 antibodies among health care workers and frontline workers in Mumbai qualitatively and quantitatively and observe the change in antibody levels after 6 months. Material and Methods: This longitudinal study was conducted over 9 months in two phases among 1544 healthcare workers (HCWs) and 1555 frontline workers (FLWs) aged above 18 years in Mumbai, Maharashtra, India. Participants' blood samples were analyzed using the SARS-CoV-2 IgG-II Quant assay for the qualitative and quantitative determination of IgG antibodies to SARS-CoV-2. A follow-up was done after 6 months. Results: A total of 2733 (88.2%) of the 3099 participants were followed up in Phase II, which included 1370 (50.1%) FLWs and 1363 (49.9%) HCWs. The study found a seropositivity rate of 99.9% with a significantly higher antibody titre in BEST (public transport) workers, those vaccinated with precautionary doses, those vaccinated with precautionary doses with a history of confirmed COVID-19 disease, and participants over 45 years. Conclusions: The study findings indicate a widespread seroconversion against COVID-19 and a beneficial effect of precautionary dose in addition to two doses of the COVID-19 vaccine. The role of subclinical infection needs to be explored.
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