BMC Medicine (Nov 2021)

SARS-CoV-2 exposure in Malawian blood donors: an analysis of seroprevalence and variant dynamics between January 2020 and July 2021

  • Jonathan Mandolo,
  • Jacquline Msefula,
  • Marc Y. R. Henrion,
  • Comfort Brown,
  • Brewster Moyo,
  • Aubrey Samon,
  • Thandeka Moyo-Gwete,
  • Zanele Makhado,
  • Frances Ayres,
  • Thopisang Motlou,
  • Nonkululeko Mzindle,
  • Newton Kalata,
  • Adamson S. Muula,
  • Gaurav Kwatra,
  • Natasha Nsamala,
  • Andrew Likaka,
  • Thom Mfune,
  • Penny L. Moore,
  • Bridon Mbaya,
  • Neil French,
  • Robert S. Heyderman,
  • Todd Swarthout,
  • Kondwani C. Jambo

DOI
https://doi.org/10.1186/s12916-021-02187-y
Journal volume & issue
Vol. 19, no. 1
pp. 1 – 10

Abstract

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Abstract Background By August 2021, the COVID-19 pandemic has been less severe in sub-Saharan Africa than elsewhere. In Malawi, there have been three subsequent epidemic waves. We therefore aimed to describe the dynamics of SARS-CoV-2 exposure in Malawi. Methods We measured the seroprevalence of anti-SARS-CoV-2 antibodies amongst randomly selected blood transfusion donor sera in Malawi from January 2020 to July 2021 using a cross-sectional study design. In a subset, we also assessed in vitro neutralisation against the original variant (D614G WT) and the Beta variant. Results A total of 5085 samples were selected from the blood donor database, of which 4075 (80.1%) were aged 20–49 years. Of the total, 1401 were seropositive. After adjustment for assay characteristics and applying population weights, seropositivity reached peaks in October 2020 (18.5%) and May 2021 (64.9%) reflecting the first two epidemic waves. Unlike the first wave, both urban and rural areas had high seropositivity in the second wave, Balaka (rural, 66.2%, April 2021), Blantyre (urban, 75.6%, May 2021), Lilongwe (urban, 78.0%, May 2021), and Mzuzu (urban, 74.6%, April 2021). Blantyre and Mzuzu also show indications of the start of a third pandemic wave with seroprevalence picking up again in July 2021 (Blantyre, 81.7%; Mzuzu, 71.0%). More first wave sera showed in vitro neutralisation activity against the original variant (78% [7/9]) than the beta variant (22% [2/9]), while more second wave sera showed neutralisation activity against the beta variant (75% [12/16]) than the original variant (63% [10/16]). Conclusion The findings confirm extensive SARS-CoV-2 exposure in Malawi over two epidemic waves with likely poor cross-protection to reinfection from the first on the second wave. The dynamics of SARS-CoV-2 exposure will therefore need to be taken into account in the formulation of the COVID-19 vaccination policy in Malawi and across the region. Future studies should use an adequate sample size for the assessment of neutralisation activity across a panel of SARS-CoV-2 variants of concern/interest to estimate community immunity.

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