Serial population-based sero-surveys for COVID-19 in two neighborhoods of Karachi, Pakistan

Document Type



Paediatrics and Child Health


Objective: To determine population-based estimates of COVID-19 in a densely populated urban community of Karachi, Pakistan.
Methods: Three cross-sectional surveys were conducted in April, June and August in low- and high-transmission neighborhoods. Participants were randomly selected to provide blood for Elecsys® immunoassay for detection of anti-SARS-CoV-2 antibodies. Bayesian regression model was used to estimate seroprevalence after adjusting for the demographic characteristics of each district RESULTS: We enrolled 3005 participants from 623 households. In Phase 2, adjusted seroprevalence was estimated as 8.7% (95% CI 5.1-13.1) and 15.1% (95% CI 9.4 -21.7) in low and high transmission areas respectively, compared to 0.2% (95% CI 0-0.7) and 0.4% (95% CI 0 - 1.3) in Phase 1. In Phase 3, it was 12.8% (95% CI 8.3 - 17.7) and 21.5% (95% CI 15.6-28) in low and high transmission areas, respectively. CRI was 0.31 (95% CI 0.16-0.47) and 0.41(95% CI 0.28-0.52) in low and high transmission neighborhoods respectively in Phase 2. Similar trends were observed in Phase 3. Only 5.4% of participants who tested positive for COVID-19 were symptomatic. IFR was 1.66%, 0.37% and 0.26% in Phases 1, 2 and 3 respectively.
Conclusion: Continuing rounds of seroprevalence studies will help us better understand secular trends and extent of infection during the course of the pandemic.


Volume, issue, and pagination are not provided by the author/publisher


International Journal of Infectious Diseases