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. 2025 Apr 11;16(1):758.
doi: 10.4102/jphia.v16i1.758. eCollection 2025.

COVID-19 severity and vaccine effectiveness in Malawi: A test-negative case-control study

Clara Sambani  1 , Victor Chikwapulo  2 , Regina Mankhamba  1 , Tonny Muwonge  3 , Mavuto Thomas  4 , Baxter Salatiel  1 , Edna Mandala  5 , Leah Mbabazi  6 , Suzan Nakasendwa  6 , Rodgers R Ayebare  6 , Collins Mitambo  1 , Matthew Kagoli  1 , Mabvuto Chiwaula  1 , Dzinkambani Kambalame  1 , Triza Chirwa  1 , Liness Chinyamunyamu  7 , Tamrat Shaweno  8 , Nebiyu Dereje  8 , Tajudeen Raji  8 , Francis Kakooza  9 , Mosoka P Fallah  8 , Evelyn C Banda  1 , Abigail Kazembe  5   10 , Mitch Matoga  11
Affiliations

COVID-19 severity and vaccine effectiveness in Malawi: A test-negative case-control study

Clara Sambani et al. J Public Health Afr. .

Abstract

Background: COVID-19 vaccines were administered globally, and Malawi commenced vaccination on 11 March 2021.

Aim: This study assessed the real-world effectiveness of COVID-19 vaccines and factors associated with disease severity and mortality in Malawi.

Setting: A facility-based case-control study within the largest referral hospitals.

Methods: Cases (COVID-19 positive) were matched 1:1 with controls based on age, sex and testing date. Interviews via phone focused on COVID-19 testing and vaccination, underlying conditions and disease outcomes. Analysed using STATA 17, the exposure of interest was vaccination status. For vaccine effectiveness (VE), conditional logistic regression modelling was used, while disease severity and management were analysed using binary logistic regression.

Results: The unvaccinated were at 53.3%, and 35.8% were fully vaccinated and/or received a booster. The VE among the fully and partially vaccinated was 10% (95% CI: -26.2, 35.81) and 31.8% (95% CI: -9.91, 57.72), respectively compared to the unvaccinated. Most of the COVID-19 patients (87.8%) were not hospitalised. Underlying chronic conditions and a previous positive COVID-19 test were associated with severe disease (aOR: 3.54, 95% CI: 1.65, 7.61 and aOR: 2.73, 95% CI: 1.13, 7.61, respectively); however, these odds were not different by vaccination status.

Conclusion: The VE was low and severe disease was linked with chronic illnesses and previous positive COVID-19 tests. Efforts to promote vaccination through education and access should be enhanced, particularly for those with underlying chronic conditions.

Contribution: The findings can inform strategies on prioritisation for disease vaccination and improving patient outcomes.

Keywords: COVID-19; Malawi; effectiveness; hospitalisation; risk; severity; vaccine.

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Conflict of interest statement

The author reported that they received funding from the Saving Lives and Livelihoods (SLL) programme, an initiative of Africa Centers for Disease Control and Prevention (CDC) and the Mastercard Foundation which may be affected by the research reported in the enclosed publication. The author has disclosed those interests fully and has implemented an approved plan for managing any potential conflicts arising from their involvement. The terms of these funding arrangements have been reviewed and approved by the affiliated university in accordance with its policy on objectivity in research. N.D. is the Editor-in-Chief of the Journal of Public Health in Africa and T.S serves as an editorial board member of this journal. The peer review process for this submission was handled independently, and the authors had no involvement in the editorial decision-making process for this article. The authors has no other competing interests to declare.

Figures

FIGURE 1
FIGURE 1
Vaccination status among study participants in Malawi at the time of COVID-19 testing.
See this image and copyright information in PMC

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