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Characterizing the evolving SARS-CoV-2 seroprevalence in urban and rural Malawi between February 2021 and April 2022: a population-based cohort study

Research output: Contribution to Journal/MagazineJournal articlepeer-review

  • Louis Banda
  • Antonia Ho
  • Stephen Kasenda
  • Jonathan M Read
  • Chris Jewell
  • Alison Price
  • Estelle McLean
  • Albert Dube
  • David Chaima
  • Lyson Samikwa
  • Tonney S Nyirenda
  • Ellen C Hughes
  • Brian J Willett
  • Annie Chauma Mwale
  • Abena S Amoah
  • Amelia Crampin
<mark>Journal publication date</mark>1/12/2023
<mark>Journal</mark>International Journal of Infectious Diseases
Number of pages8
Pages (from-to)118-125
Publication StatusPublished
Early online date14/11/23
<mark>Original language</mark>English


Objectives: This study aimed to investigate the changing SARS-CoV-2 seroprevalence and associated health and sociodemographic factors in Malawi between February 2021 and April 2022. Methods: In total, four 3-monthly serosurveys were conducted within a longitudinal population-based cohort in rural Karonga District and urban Lilongwe, testing for SARS-CoV-2 S1 immunoglobulin (Ig)G antibodies using an enzyme-linked immunosorbent assay. Population seroprevalence was estimated in all and unvaccinated participants. Bayesian mixed-effects logistic models estimated the odds of seropositivity in the first survey, and of seroconversion between surveys, adjusting for age, sex, occupation, location, and assay sensitivity/specificity. Results: Of the 2005 participants (Karonga, n = 1005; Lilongwe, n = 1000), 55.8% were female and median age was 22.7 years. Between Surveys (SVY) 1 and 4, population-weighted SARS-CoV-2 seroprevalence increased from 26.3% to 89.2% and 46.4% to 93.9% in Karonga and Lilongwe, respectively. At SVY4, seroprevalence did not differ by COVID-19 vaccination status in adults, except for those aged 30+ years in Karonga (unvaccinated: 87.4%, 95% credible interval 79.3-93.0%; two doses: 98.1%, 94.8-99.5%). Location and age were associated with seroconversion risk. Individuals with hybrid immunity had higher SARS-CoV-2 seropositivity and antibody titers, than those infected. Conclusion: High SARS-CoV-2 seroprevalence combined with low morbidity and mortality indicate that universal vaccination is unnecessary at this stage of the pandemic, supporting change in national policy to target at-risk groups.