SARS-CoV-2 prevalence and immunity: a hospital-based study from Malawi

https://doi.org/10.1016/j.ijid.2021.12.336Get rights and content
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Highlights

  • Early-stage, large-scale SARS-CoV-2 serosurvey combining PCR and sVNT in Africa

  • SARS-CoV-2 prevalence and immunity is grossly underestimated by official surveillance

  • Asymptomatic and subclinical infection and transmission are high

  • targeted risk group approach preferable over undirected lockdown measures

  • Conduction of sVNT is feasible even with limited laboratory infrastructure

Abstract

Background

COVID-19 transmission and disease dynamics in sub-Saharan Africa are not well understood. Our study aims to provide insight into COVID-19 epidemiology in Malawi by estimating SARS-CoV-2 prevalence and immunity after SARS-CoV-2 infection in a hospital-based setting.

Methods

We conducted a hospital-based, convenience sampling, cross-sectional survey for SARS-CoV-2 in Lilongwe, Malawi. Participants answered a questionnaire and were tested for SARS-CoV-2 by enzyme-linked immunosorbent assay and real-time reverse-transcription polymerase chain reaction (RT-PCR). A surrogate virus neutralization test (sVNT) was performed in seropositive samples to estimate immunity. Poisson regression was used to assess SARS-CoV-2 point prevalence association with demographic and behavioral variables.

Findings

The study included 930 participants. We found a combined point prevalence of 10.1%. Separately analyzed, RT-PCR positivity was 2.0%, and seropositivity was 9.3%. Of tested seropositive samples, 90.1% were sVNT positive. We found a high rate (45.7%) of asymptomatic SARS-CoV-2 infection. SARS-CoV-2 point prevalence was significantly associated with being a healthcare worker.

Interpretation

Our study suggests that official data underestimate COVID-19 transmission. Using sVNTs to estimate immunity in Malawi is feasible and revealed considerable post-infection immunity in our cohort. Subclinical infection and transmission are probably a game-changer in surveillance, mitigation and vaccination strategies.

Keywords

serosurvey
COVID-19
prevalence
immunity
Malawi
Africa

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