Sustained natural immunity following SARS-CoV-2 infection against severe COVID-19 outcomes and symptomatic reinfection: analyses of national data for Brazil and Scotland
Objectives SARS-CoV-2 infection provides protection against reinfection and severe COVID-19 disease; however, this protective effect may diminish over time. We assessed waning of natural immunity conferred by previous infection against severe disease and symptomatic reinfection in Brazil and Scotlan...
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BMJ Publishing Group
2025-07-01
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| Online Access: | https://bmjopen.bmj.com/content/15/7/e104057.full |
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| author | Aziz Sheikh Neil Pearce Mauricio L Barreto Chris Robertson Srinivasa Vittal Katikireddi Syed Ahmar Shah Kirsten J Hainey Thiago Cerqueira-Silva Manoel Barral-Netto Tristan Millington Fasih Haider Vincius de Araujo Oliveira Viviane Sampaio Boaventura |
| author_facet | Aziz Sheikh Neil Pearce Mauricio L Barreto Chris Robertson Srinivasa Vittal Katikireddi Syed Ahmar Shah Kirsten J Hainey Thiago Cerqueira-Silva Manoel Barral-Netto Tristan Millington Fasih Haider Vincius de Araujo Oliveira Viviane Sampaio Boaventura |
| author_sort | Aziz Sheikh |
| collection | DOAJ |
| description | Objectives SARS-CoV-2 infection provides protection against reinfection and severe COVID-19 disease; however, this protective effect may diminish over time. We assessed waning of natural immunity conferred by previous infection against severe disease and symptomatic reinfection in Brazil and Scotland.Design We undertook a test-negative design study and nested case–control analysis to estimate waning of natural immunity against severe COVID-19 outcomes and symptomatic reinfection using national linked datasets. We used logistic regression to estimate ORs with 95% CIs. A stratified analysis assessed immunity during the Omicron dominant period in Brazil.Setting and participants We included data from the adult populations of Brazil and Scotland from 1 June 2020 to 30 April 2022.Outcome measures Severe COVID-19 was defined as hospitalisation or death. Reinfection was defined as reverse-transcriptase PCR or rapid antigen test confirmed at least 120 days after primary infection.Results From Brazil, we included 30 881 873 tests and 1 301 665 severe COVID-19 outcomes, and from Scotland, we included 1 520 201 tests and 7988 severe COVID-19 outcomes. Against severe outcomes, sustained protection was observed for at least 12 months after primary SARS-CoV-2 infection with little evidence of waning: <6 months postprimary infection: Brazil OR 0.10 (95% CI 0.09 to 0.11), Scotland OR 0.01 (95% CI 0.00 to 0.05); >12 months postprimary infection: Brazil OR 0.12 (95% CI 0.10 to 0.14), Scotland OR 0.03 (95% CI 0.02 to 0.04). For symptomatic reinfection, Brazilian data demonstrated evidence of waning in the 12 months following primary infection, although some residual protection remained beyond 12 months: <6 months postprimary infection: OR 0.19 (95% CI 0.19 to 0.20); >12 months postprimary infection: OR 0.42 (95% CI 0.40 to 0.43). The greatest reduction in risk of SARS-CoV-2 infection was in individuals with hybrid immunity (history of previous infection and vaccination), with sustained protection against severe outcomes at 12 months postprimary infection. During the Omicron dominant period in Brazil, odds of symptomatic reinfection were higher and increased more quickly over time when compared with the overall study period, although protection against severe outcomes was sustained at 12 months postprimary infection (whole study: OR 0.12 (95% CI 0.10 to 0.14); Omicron phase: OR 0.15 (95% CI 0.12 to 0.19)).Conclusion Cross-national analyses demonstrate sustained protection against severe COVID-19 disease for at least 12 months following natural SARS-CoV-2 infection, with vaccination further enhancing protection. Protection against symptomatic reinfection was lower with evidence of waning, but there remained a protective effect beyond 12 months from primary infection. |
| format | Article |
| id | doaj-art-3224761a3e944e6f9da2dba1b610ebc0 |
| institution | Matheson Library |
| issn | 2044-6055 |
| language | English |
| publishDate | 2025-07-01 |
| publisher | BMJ Publishing Group |
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| series | BMJ Open |
| spelling | doaj-art-3224761a3e944e6f9da2dba1b610ebc02025-07-17T07:40:11ZengBMJ Publishing GroupBMJ Open2044-60552025-07-0115710.1136/bmjopen-2025-104057Sustained natural immunity following SARS-CoV-2 infection against severe COVID-19 outcomes and symptomatic reinfection: analyses of national data for Brazil and ScotlandAziz Sheikh0Neil Pearce1Mauricio L Barreto2Chris Robertson3Srinivasa Vittal Katikireddi4Syed Ahmar Shah5Kirsten J Hainey6Thiago Cerqueira-Silva7Manoel Barral-Netto8Tristan Millington9Fasih Haider10Vincius de Araujo Oliveira11Viviane Sampaio Boaventura12Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UKMedical Statistics, London School of Hygiene & Tropical Medicine, London, UKCenter of Data and Knowledge Integration for Health (Cidacs), Fiocruz, Salvador, BrazilPublic Health Scotland, Glasgow, UKMRC/CSO Social and Public Health Sciences Unit, University of Glasgow, Glasgow, UKUsher Institute, the University of Edinburgh, Edinburgh, UKMRC/CSO Social and Public Health Sciences Unit, University of Glasgow, Glasgow, UKLaboratório de Medicina e Saúde Pública de Precisão, Fundação Oswaldo Cruz, Salvador, BrazilLaboratório de Medicina e Saúde Pública de Precisão, Fundação Oswaldo Cruz, Salvador, BrazilPublic Health Scotland, Glasgow, UKUsher Institute, the University of Edinburgh, Edinburgh, UKCenter of Data and Knowledge Integration for Health (Cidacs), Fiocruz, Salvador, BrazilLaboratório de Medicina e Saúde Pública de Precisão, Fundação Oswaldo Cruz, Salvador, BrazilObjectives SARS-CoV-2 infection provides protection against reinfection and severe COVID-19 disease; however, this protective effect may diminish over time. We assessed waning of natural immunity conferred by previous infection against severe disease and symptomatic reinfection in Brazil and Scotland.Design We undertook a test-negative design study and nested case–control analysis to estimate waning of natural immunity against severe COVID-19 outcomes and symptomatic reinfection using national linked datasets. We used logistic regression to estimate ORs with 95% CIs. A stratified analysis assessed immunity during the Omicron dominant period in Brazil.Setting and participants We included data from the adult populations of Brazil and Scotland from 1 June 2020 to 30 April 2022.Outcome measures Severe COVID-19 was defined as hospitalisation or death. Reinfection was defined as reverse-transcriptase PCR or rapid antigen test confirmed at least 120 days after primary infection.Results From Brazil, we included 30 881 873 tests and 1 301 665 severe COVID-19 outcomes, and from Scotland, we included 1 520 201 tests and 7988 severe COVID-19 outcomes. Against severe outcomes, sustained protection was observed for at least 12 months after primary SARS-CoV-2 infection with little evidence of waning: <6 months postprimary infection: Brazil OR 0.10 (95% CI 0.09 to 0.11), Scotland OR 0.01 (95% CI 0.00 to 0.05); >12 months postprimary infection: Brazil OR 0.12 (95% CI 0.10 to 0.14), Scotland OR 0.03 (95% CI 0.02 to 0.04). For symptomatic reinfection, Brazilian data demonstrated evidence of waning in the 12 months following primary infection, although some residual protection remained beyond 12 months: <6 months postprimary infection: OR 0.19 (95% CI 0.19 to 0.20); >12 months postprimary infection: OR 0.42 (95% CI 0.40 to 0.43). The greatest reduction in risk of SARS-CoV-2 infection was in individuals with hybrid immunity (history of previous infection and vaccination), with sustained protection against severe outcomes at 12 months postprimary infection. During the Omicron dominant period in Brazil, odds of symptomatic reinfection were higher and increased more quickly over time when compared with the overall study period, although protection against severe outcomes was sustained at 12 months postprimary infection (whole study: OR 0.12 (95% CI 0.10 to 0.14); Omicron phase: OR 0.15 (95% CI 0.12 to 0.19)).Conclusion Cross-national analyses demonstrate sustained protection against severe COVID-19 disease for at least 12 months following natural SARS-CoV-2 infection, with vaccination further enhancing protection. Protection against symptomatic reinfection was lower with evidence of waning, but there remained a protective effect beyond 12 months from primary infection.https://bmjopen.bmj.com/content/15/7/e104057.full |
| spellingShingle | Aziz Sheikh Neil Pearce Mauricio L Barreto Chris Robertson Srinivasa Vittal Katikireddi Syed Ahmar Shah Kirsten J Hainey Thiago Cerqueira-Silva Manoel Barral-Netto Tristan Millington Fasih Haider Vincius de Araujo Oliveira Viviane Sampaio Boaventura Sustained natural immunity following SARS-CoV-2 infection against severe COVID-19 outcomes and symptomatic reinfection: analyses of national data for Brazil and Scotland BMJ Open |
| title | Sustained natural immunity following SARS-CoV-2 infection against severe COVID-19 outcomes and symptomatic reinfection: analyses of national data for Brazil and Scotland |
| title_full | Sustained natural immunity following SARS-CoV-2 infection against severe COVID-19 outcomes and symptomatic reinfection: analyses of national data for Brazil and Scotland |
| title_fullStr | Sustained natural immunity following SARS-CoV-2 infection against severe COVID-19 outcomes and symptomatic reinfection: analyses of national data for Brazil and Scotland |
| title_full_unstemmed | Sustained natural immunity following SARS-CoV-2 infection against severe COVID-19 outcomes and symptomatic reinfection: analyses of national data for Brazil and Scotland |
| title_short | Sustained natural immunity following SARS-CoV-2 infection against severe COVID-19 outcomes and symptomatic reinfection: analyses of national data for Brazil and Scotland |
| title_sort | sustained natural immunity following sars cov 2 infection against severe covid 19 outcomes and symptomatic reinfection analyses of national data for brazil and scotland |
| url | https://bmjopen.bmj.com/content/15/7/e104057.full |
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