High SARS-CoV-2 incidence and asymptomatic fraction during Delta and Omicron BA.1 waves in The Gambia

Little is known about SARS-CoV-2 infection risk in African countries with high levels of infection-driven immunity and low vaccine coverage. We conducted a prospective cohort study of 349 participants from 52 households in The Gambia between March 2021 and June 2022, with routine weekly SARS-CoV-2 R...

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Published in:Nature communications Vol. 15; no. 1; p. 3814
Main Authors: Jarju, Sheikh, Wenlock, Rhys D., Danso, Madikoi, Jobe, Dawda, Jagne, Ya Jankey, Darboe, Alansana, Kumado, Michelle, Jallow, Yusupha, Touray, Mamlie, Ceesay, Ebrima A., Gaye, Hoja, Gaye, Biran, Tunkara, Abdoulie, Kandeh, Sheriff, Gomes, Marie, Sylva, Ellen Lena, Toure, Fatoumata, Hornsby, Hailey, Lindsey, Benjamin B., Nicklin, Martin J., Sayers, Jon R., Sesay, Abdul K., Kucharski, Adam, Hodgson, David, Kampmann, Beate, de Silva, Thushan I.
Format: Journal Article
Language:English
Published: London Nature Publishing Group UK 07-05-2024
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Summary:Little is known about SARS-CoV-2 infection risk in African countries with high levels of infection-driven immunity and low vaccine coverage. We conducted a prospective cohort study of 349 participants from 52 households in The Gambia between March 2021 and June 2022, with routine weekly SARS-CoV-2 RT-PCR and 6-monthly SARS-CoV-2 serology. Attack rates of 45% and 57% were seen during Delta and Omicron BA.1 waves respectively. Eighty-four percent of RT-PCR-positive infections were asymptomatic. Children under 5-years had a lower incidence of infection than 18-49-year-olds. One prior SARS-CoV-2 infection reduced infection risk during the Delta wave only, with immunity from ≥2 prior infections required to reduce the risk of infection with early Omicron lineage viruses. In an African population with high levels of infection-driven immunity and low vaccine coverage, we find high attack rates during SARS-CoV-2 waves, with a high proportion of asymptomatic infections and young children remaining relatively protected from infection. Many low- and middle-income countries, including The Gambia, had low COVID-19 vaccination coverage during the emergence of the Delta and Omicron variants. Here, the authors perform a prospective household cohort study in the Gambia to investigate the dynamics of SARS-Cov-2 infection in this setting.
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ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-024-48098-3