Test negative case-control study of COVID-19 vaccine effectiveness for symptomatic SARS-CoV-2 infection among healthcare workers: Zambia, 2021-2022.
Oliver MwesoJohn SimwanzaWarren MalamboDabwitso BandaSombo FwoloshiNyambe SinyangeYoung M YooLeora R FeldsteinMuzala KapinaLloyd B MulengaMazyanga Mazaba LiweweKunda MusondaNathan KapataFrancis Dien MwansaSimon AgoloryPatricia BoboJonas HinesRoma ChilengiPublished in: BMJ open (2023)
COVID-19 vaccines were effective in reducing symptomatic SARS-CoV-2 among Zambian HCWs when the Delta variant was circulating but not when Omicron was circulating. This could be related to immune evasive characteristics and/or waning immunity. These findings support accelerating COVID-19 booster dosing with bivalent vaccines as part of the vaccination programme to reduce COVID-19 in Zambia.