Real-world effectiveness of Ad26.COV2.S or BNT162b2 booster vaccines against severe COVID-19 in adults who received a primary dose of Ad26.COV2.S in South Africa during the Delta period: A retrospective cohort study using medical scheme data
Background. From March 2020 to June 2022, South Africa (SA) confronted successive waves of COVID‐19, each linked to emerging SARS‐CoV‐2 variants. Vaccines played a critical role in preventing severe disease and death, but as new SARS‐CoV‐2 variants emerged, with increasing breakthrough infectio...
Saved in:
| Main Authors: | , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
South African Medical Association
2025-08-01
|
| Series: | South African Medical Journal |
| Subjects: | |
| Online Access: | https://samajournals.co.za/index.php/samj/article/view/2532 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1849406728287813632 |
|---|---|
| author | L Fairall N Yende-Zuma Tarylee Reddy N Garrett A Goga S Bennet N Folb I Seocharan S Mametja M Semenya S R N Simelane L-G G E Gray |
| author_facet | L Fairall N Yende-Zuma Tarylee Reddy N Garrett A Goga S Bennet N Folb I Seocharan S Mametja M Semenya S R N Simelane L-G G E Gray |
| author_sort | L Fairall |
| collection | DOAJ |
| description |
Background. From March 2020 to June 2022, South Africa (SA) confronted successive waves of COVID‐19, each linked to emerging SARS‐CoV‐2 variants. Vaccines played a critical role in preventing severe disease and death, but as new SARS‐CoV‐2 variants emerged, with increasing breakthrough infections, questions arose about the real‐world effectiveness of first‐generation vaccines containing the ancestral strain against evolving variants including Delta and Omicron BA.1 and BA.4/5 SARS‐CoV‐2.
Objectives. To assess the real‐world effectiveness of ancestral strain booster doses (either Ad26.COV2.S or BNT162b2) in preventing severe COVID‐19 outcomes, including hospitalisation, admission to critical care and death, among essential workers in SA who received a primary dose of Ad26.COV2.S against emerging SARS‐CoV‐2 variants.
Methods. A retrospective cohort study was conducted using data from a large private health insurance scheme. Individuals who received a single dose of Ad26.COV2.S as their primary vaccination were included. Time‐varying Cox regression models were used to assess the effectiveness of boosting with either Ad26.COV2.S or BNT162b2 v. not boosting against severe COVID‐19 outcomes associated with emerging variants, adjusting for various demographic and clinical factors.
Results. By August 2021, a total of 407 961 individuals received a first dose of Ad26.COV2.S, of whom 350 688 were eligible for and 332 286 included in the vaccine effectiveness (VE) analysis. Of these, 206 359 (62%) received no further doses, while 113 957 (34%) received a second dose of Ad26.COV2.S and 11 970 (4%) received a second dose of BNT162b2 by August 2022. During the follow‐up period (November 2021 ‐ August 2022), 1 125 COVID‐19‐related hospital admissions, 198 admissions to critical care and 41 COVID‐19‐related deaths were recorded. Adjusted relative VE against severe outcomes was 34% (95% confidence interval (CI) 19 ‐ 45) for hospital admission, 51% (95% CI 22 ‐ 70) for critical care admission, and 89% (95% CI 13 ‐ 98) for COVID‐19‐ related death.
Conclusion. While most participants remained unboosted, administration of either ancestral strain Ad26.COV2.S or BNT162b2 vaccination provided protection against severe COVID‐19 outcomes among essential workers in SA during the dominance of the Omicron BA.1 and BA.4/5 variants, demonstrating cross‐strain protection.
|
| format | Article |
| id | doaj-art-59e8c28dae9f4d1b8a5e5c0867b71c1e |
| institution | Kabale University |
| issn | 0256-9574 2078-5135 |
| language | English |
| publishDate | 2025-08-01 |
| publisher | South African Medical Association |
| record_format | Article |
| series | South African Medical Journal |
| spelling | doaj-art-59e8c28dae9f4d1b8a5e5c0867b71c1e2025-08-20T03:36:18ZengSouth African Medical AssociationSouth African Medical Journal0256-95742078-51352025-08-01115710.7196/SAMJ.2025.v115i7.2532Real-world effectiveness of Ad26.COV2.S or BNT162b2 booster vaccines against severe COVID-19 in adults who received a primary dose of Ad26.COV2.S in South Africa during the Delta period: A retrospective cohort study using medical scheme dataL Fairall0N Yende-Zuma1Tarylee Reddy2N Garrett3A Goga4S Bennet5N Folb6I Seocharan7S Mametja8M Semenya9S R N Simelane10L-G11G E Gray12School of Life Course and Population Sciences, Faculty of Life Sciences and Medicine, King’s College London, UK; Knowledge Translation Unit, Department of Medicine, Faculty of Health Sciences, University of Cape Town, South AfricaBiostatistics Research Unit, South African Medical Research Council, Durban, South Africa; Centre for the AIDS Programme of Research in South Africa (CAPRISA), Nelson R Mandela School of Medicine, University of KwaZulu-Natal, Durban, South AfricaBiostatistics Research Unit, South African Medical Research Council, Durban, South AfricaCentre for the AIDS Programme of Research in South Africa (CAPRISA), Nelson R Mandela School of Medicine, University of KwaZulu-Natal, Durban, South Africa; Discipline of Public Health Medicine, School of Nursing and Public Health, University of KwaZulu-Natal, Durban, South AfricaHIV and other Infectious Diseases Research Unit, South African Medical Research Council, Durban, South Africa; Department of Paediatrics and Child Health, School of Medicine, University of Pretoria, South AfricaMedscheme, Cape Town, South AfricaMedscheme, Cape Town, South AfricaBiostatistics Research Unit, South African Medical Research Council, Durban, South AfricaGovernment Employees Medical Scheme, Pretoria, South AfricaGovernment Employees Medical Scheme, Pretoria, South AfricaKnowledge Translation Unit, Department of Medicine, Faculty of Health Sciences, University of Cape Town, South Africa; Health Foundation of South Africa, Cape Town, South AfricaDesmond Tutu HIV Centre, Department of Medicine, Faculty of Health Sciences, University of Cape Town, South AfricaSouth African Medical Research Council, Cape Town, South Africa Background. From March 2020 to June 2022, South Africa (SA) confronted successive waves of COVID‐19, each linked to emerging SARS‐CoV‐2 variants. Vaccines played a critical role in preventing severe disease and death, but as new SARS‐CoV‐2 variants emerged, with increasing breakthrough infections, questions arose about the real‐world effectiveness of first‐generation vaccines containing the ancestral strain against evolving variants including Delta and Omicron BA.1 and BA.4/5 SARS‐CoV‐2. Objectives. To assess the real‐world effectiveness of ancestral strain booster doses (either Ad26.COV2.S or BNT162b2) in preventing severe COVID‐19 outcomes, including hospitalisation, admission to critical care and death, among essential workers in SA who received a primary dose of Ad26.COV2.S against emerging SARS‐CoV‐2 variants. Methods. A retrospective cohort study was conducted using data from a large private health insurance scheme. Individuals who received a single dose of Ad26.COV2.S as their primary vaccination were included. Time‐varying Cox regression models were used to assess the effectiveness of boosting with either Ad26.COV2.S or BNT162b2 v. not boosting against severe COVID‐19 outcomes associated with emerging variants, adjusting for various demographic and clinical factors. Results. By August 2021, a total of 407 961 individuals received a first dose of Ad26.COV2.S, of whom 350 688 were eligible for and 332 286 included in the vaccine effectiveness (VE) analysis. Of these, 206 359 (62%) received no further doses, while 113 957 (34%) received a second dose of Ad26.COV2.S and 11 970 (4%) received a second dose of BNT162b2 by August 2022. During the follow‐up period (November 2021 ‐ August 2022), 1 125 COVID‐19‐related hospital admissions, 198 admissions to critical care and 41 COVID‐19‐related deaths were recorded. Adjusted relative VE against severe outcomes was 34% (95% confidence interval (CI) 19 ‐ 45) for hospital admission, 51% (95% CI 22 ‐ 70) for critical care admission, and 89% (95% CI 13 ‐ 98) for COVID‐19‐ related death. Conclusion. While most participants remained unboosted, administration of either ancestral strain Ad26.COV2.S or BNT162b2 vaccination provided protection against severe COVID‐19 outcomes among essential workers in SA during the dominance of the Omicron BA.1 and BA.4/5 variants, demonstrating cross‐strain protection. https://samajournals.co.za/index.php/samj/article/view/2532COVID-19SARS-CoV-2vaccine effectivenessAd26.COV2.S vaccinevariants of concernancestral vaccine |
| spellingShingle | L Fairall N Yende-Zuma Tarylee Reddy N Garrett A Goga S Bennet N Folb I Seocharan S Mametja M Semenya S R N Simelane L-G G E Gray Real-world effectiveness of Ad26.COV2.S or BNT162b2 booster vaccines against severe COVID-19 in adults who received a primary dose of Ad26.COV2.S in South Africa during the Delta period: A retrospective cohort study using medical scheme data South African Medical Journal COVID-19 SARS-CoV-2 vaccine effectiveness Ad26.COV2.S vaccine variants of concern ancestral vaccine |
| title | Real-world effectiveness of Ad26.COV2.S or BNT162b2 booster vaccines against severe COVID-19 in adults who received a primary dose of Ad26.COV2.S in South Africa during the Delta period: A retrospective cohort study using medical scheme data |
| title_full | Real-world effectiveness of Ad26.COV2.S or BNT162b2 booster vaccines against severe COVID-19 in adults who received a primary dose of Ad26.COV2.S in South Africa during the Delta period: A retrospective cohort study using medical scheme data |
| title_fullStr | Real-world effectiveness of Ad26.COV2.S or BNT162b2 booster vaccines against severe COVID-19 in adults who received a primary dose of Ad26.COV2.S in South Africa during the Delta period: A retrospective cohort study using medical scheme data |
| title_full_unstemmed | Real-world effectiveness of Ad26.COV2.S or BNT162b2 booster vaccines against severe COVID-19 in adults who received a primary dose of Ad26.COV2.S in South Africa during the Delta period: A retrospective cohort study using medical scheme data |
| title_short | Real-world effectiveness of Ad26.COV2.S or BNT162b2 booster vaccines against severe COVID-19 in adults who received a primary dose of Ad26.COV2.S in South Africa during the Delta period: A retrospective cohort study using medical scheme data |
| title_sort | real world effectiveness of ad26 cov2 s or bnt162b2 booster vaccines against severe covid 19 in adults who received a primary dose of ad26 cov2 s in south africa during the delta period a retrospective cohort study using medical scheme data |
| topic | COVID-19 SARS-CoV-2 vaccine effectiveness Ad26.COV2.S vaccine variants of concern ancestral vaccine |
| url | https://samajournals.co.za/index.php/samj/article/view/2532 |
| work_keys_str_mv | AT lfairall realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT nyendezuma realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT taryleereddy realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT ngarrett realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT agoga realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT sbennet realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT nfolb realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT iseocharan realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT smametja realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT msemenya realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT srnsimelane realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT lg realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata AT gegray realworldeffectivenessofad26cov2sorbnt162b2boostervaccinesagainstseverecovid19inadultswhoreceivedaprimarydoseofad26cov2sinsouthafricaduringthedeltaperiodaretrospectivecohortstudyusingmedicalschemedata |