@article{Kassanjee2024a,
abstract = {There are few data on the real-world effectiveness of COVID-19 vaccines and boosting in Africa, which experienced widespread SARS-CoV-2 infection before vaccine availability. We assessed the association between vaccination and severe COVID-19 in the Western Cape, South Africa, in an observational cohort study of {\textgreater}2 million adults during 2020–2022. We described SARS-CoV-2 testing, COVID-19 outcomes, and vaccine uptake over time. We used multivariable cox models to estimate the association of BNT162b2 and Ad26.COV2.S vaccination with COVID-19-related hospitalization and death, adjusting for demographic characteristics, underlying health conditions, socioeconomic status proxies, and healthcare utilization. We found that by the end of 2022, 41{\%} of surviving adults had completed vaccination and 8{\%} had received a booster dose. Recent vaccination was associated with notable reductions in severe COVID-19 during periods dominated by Delta, and Omicron BA.1/2 and BA.4/5 (sub)lineages. During the latest Omicron BA.4/5 wave, within 3 months of vaccination or boosting, BNT162b2 and Ad26.COV2.S were each 84{\%} effective against death (95{\%} CIs: 57–94 and 49–95, respectively). However, distinct reductions of effectiveness occurred at longer times post completing or boosting vaccination. Results highlight the importance of continued emphasis on COVID-19 vaccination and boosting for those at high risk of severe COVID-19, even in settings with widespread infection-induced immunity.},
author = {Kassanjee, Reshma and Davies, Mary-Ann and Heekes, Alexa and Mahomed, Hassan and Hawkridge, Anthony and Morden, Erna and Jacobs, Theuns and Cohen, Cheryl and Moultrie, Harry and Lessells, Richard and {Van Der Walt}, Nicolette and Arendse, Juanita and Wolter, Nicole and Walaza, Sibongile and Jassat, Waasila and von Gottberg, Anne and Hannan, Patrick and Feikin, Daniel and Cloete, Keith and Boulle, Andrew},
doi = {10.3390/VACCINES12060628/S1},
file = {:C$\backslash$:/Users/01462563/AppData/Local/Mendeley Ltd./Mendeley Desktop/Downloaded/Kassanjee et al. - 2024 - COVID-19 Vaccine Uptake and Effectiveness by Time since Vaccination in the Western Cape Province, South Afr(2).pdf:pdf},
issn = {2076393X},
journal = {Vaccines},
keywords = {19,2,COVID,CoV,OA,SARS,South Africa,cohort,fund{\_}ack,genomics{\_}fund{\_}ack,observational,original,vaccine effectiveness},
mendeley-tags = {OA,fund{\_}ack,genomics{\_}fund{\_}ack,original},
month = {jun},
number = {6},
pages = {628},
publisher = {MDPI AG},
title = {{COVID-19 vaccine uptake and effectiveness by time since vaccination in the Western Cape province, South Africa: an observational cohort study during 2020–2022}},
url = {https://www.mdpi.com/2076-393X/12/6/628/htm https://www.mdpi.com/2076-393X/12/6/628},
volume = {12},
year = {2024}
}

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We described SARS-CoV-2 testing, COVID-19 outcomes, and vaccine uptake over time. We used multivariable cox models to estimate the association of BNT162b2 and Ad26.COV2.S vaccination with COVID-19-related hospitalization and death, adjusting for demographic characteristics, underlying health conditions, socioeconomic status proxies, and healthcare utilization. We found that by the end of 2022, 41% of surviving adults had completed vaccination and 8% had received a booster dose. Recent vaccination was associated with notable reductions in severe COVID-19 during periods dominated by Delta, and Omicron BA.1/2 and BA.4/5 (sub)lineages. During the latest Omicron BA.4/5 wave, within 3 months of vaccination or boosting, BNT162b2 and Ad26.COV2.S were each 84% effective against death (95% CIs: 57–94 and 49–95, respectively). However, distinct reductions of effectiveness occurred at longer times post completing or boosting vaccination. 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