Study finds severe disease from Omicron B.1.1529 SARS-CoV-2 infections are uncommon in under-vaccinated Malawian community

Press release 19 Jan 2023

A study, published in eClinicalMedicine (part of the The Lancet Discovery Science) examining blood serum results for people with Omicron B.1.1529 Covid infections in an under-vaccinated Malawian community, showed low levels of severe disease. 

The study was carried out by a team including researchers from Liverpool School of Tropical Medicine (LSTM) and the Malawi-Liverpool-Welcome Programme (MLW), between December 2021 and January 2022, across seven districts in Malawi. Serum samples were tested for antibodies against SARS-CoV-2, to give a fuller picture of the prevalence of the disease in the community. COVID-19 epidemiologic trends in Malawi - cases, hospitalisations, and deaths – were also collected, using the routine national COVID-19 reporting system, and analysed alongside the findings.

Serum samples were analysed from 4619 participants (57% female; 60% aged 18–50 years). Out of those people only 23% of those who were eligible (³18 years) for a vaccine had received a single dose of any COVID-19 vaccine. The overall assay-adjusted seroprevalence was 83.7% (95% confidence interval (CI), 79.3%–93.4%).

The study, supported with funding from the Bill and Melinda Gates Foundation, concluded that there had been a reduction in hospitalisations and deaths from SARS-CoV-2 infections, during the Omicron variant-dominated wave in Malawi - in the context of high SARS-CoV-2 seroprevalence and low COVID-19 vaccination coverage, indicating high infection-induced population level immunity. As reiterated by the corresponding author, Associate Professor Kondwani Jambo of LSTM and MLW, “the findings from the study suggest that COVID-19 vaccination policy in high seroprevalence settings may need to be amended from mass campaigns to more targeted vaccinations of at-risk members of a community”.

Upendo L. Mseka, Jonathan Mandolo, Kenneth Nyoni, Oscar Divala, Dzinkambani Kambalame, Daniel Mapemba, Moses Kamzati, Innocent Chibwe, Marc Y.R. Henrion, Kingsley Manda, Deus Thindwa, Memory Mvula, Bright Odala, Raphael Kamng'ona, Nelson Dzinza, Khuzwayo C. Jere, Nicholas Feasey, Antonia Ho, Abena S. Amoah, Melita Gordon, Todd D. Swarthout, Amelia Crampin, Robert S. Heyderman, Matthew Kagoli, Evelyn Chitsa-Banda, Collins Mitambo, John Phuka, Benson Chilima, Watipaso Kasambara, Kondwani C. Jambo, Annie Chauma-Mwale,
Omicron B.1.1.529 variant infections associated with severe disease are uncommon in a COVID-19 under-vaccinated, high SARS-CoV-2 seroprevalence population in Malawi,
eClinicalMedicine,Volume 56,2023,101800,ISSN 2589-5370,