Covid-19 Serosurveillance Positivity in General Population: Comparison at Different Times

Abstract

Introduction: Serological surveys estimating the cumulative incidence of the disease are powerful and effective tools for monitoring the epidemic and in determining the immunity status.
 Objectives: To compare the percentage sero-positivity for IgG antibodies against SARS-CoV2 at two different time period in the same population to understand the pandemic and predict about the immunity status of the population.
 Methods: As a part of Covid19 pandemic management, two separate population based sero-survey within a gap of 1½ months were carried in Ahmedabad city to scientifically document the progress of the Covid19 pandemic. Various demographic factors and other parameters from both the survey were compared with seropositivity for valid and precise estimation of disease situation as well as immunity status of the population.
 Results: The study documents an increase in seropositivity by 5.32% (from 17.92% to 23.24%). The seropositivity shows increasing trend with increase in the age group and the seropositivity is significantly higher among females. Overall higher seropositivity against the reported cases in the first sero-survey and the narrow increase in the seropositivity during the subsequent sero-survey inspite of high number of cases may indicate temporary status of the antibodies. This may also be due to the difference in the level of stigma, health care service delivery, service utilization and related field level situation affecting the asymptomatic/unreported case positivity.
 Conclusion: The result of seropositivity comparison indicates the scopes for further research to confirm and generate greater evidences regarding the factors affecting seropositivity.