{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,20]],"date-time":"2026-05-20T19:46:50Z","timestamp":1779306410205,"version":"3.51.4"},"reference-count":79,"publisher":"Public Library of Science (PLoS)","issue":"9","license":[{"start":{"date-parts":[[2025,9,17]],"date-time":"2025-09-17T00:00:00Z","timestamp":1758067200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:sec id=\"sec001\">\n<jats:title>Introduction<\/jats:title>\n<jats:p>Vaccines remain the most effective preventive measure against the ever-changing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. However, vaccine access remains unequal, leaving healthcare workers in low- and middle-income countries (LMICs) like Ghana at increased risk, despite early prioritisation. These inequities threaten both individual safety and the resilience of health systems. Moreover, SARS-CoV-2 infections continue to occur, particularly with emerging variants, compounding these risks. This study aimed to investigate the incidence and risk factors associated with post-vaccination SARS-CoV-2 infections among healthcare workers at a tertiary hospital in Ghana following the administration of the ChAdOx1nCoV-19 vaccine.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec002\">\n<jats:title>Method<\/jats:title>\n<jats:p>We conducted a prospective cohort study of 4252 healthcare workers aged 18 and above, who tested negative for the SARS-CoV-2, and partially or fully vaccinated with the ChAdOx1nCoV-19 vaccine at baseline. After completing the baseline questionnaire, healthcare workers were followed up for one year.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec003\">\n<jats:title>Results<\/jats:title>\n<jats:p>2283 out of the 4252 (53.7%) healthcare workers had post-vaccination infections, with an overall incidence of 95.7 cases per 100 person-years (95% CI: 91.8\u201399.7) of follow-up. The incidence of breakthrough infection was 82.0 cases per 100 person-years (95% Cl 78.0\u201386.0). In a multivariable Cox regression, age, vaccination status, occupation, clinical stations, frontline status and previous SARS-CoV-2 infections were significantly associated with post-vaccination infections. Compared to non-clinical healthcare workers, nurses (HR\u2009=\u20091.91, 95% CI: 1.69\u20132.17) and doctors (HR\u2009=\u20091.37, 95% CI: 1.24\u20131.73) had a higher risk of post-vaccination infections. Similarly, elderly individuals (HR\u2009=\u20091.04, 95% CI: 1.02\u20131.05) and those with comorbidities (HR\u2009=\u20091.86, 95% CI: 1.67\u20131.73) were more likely to develop post-vaccination infections. Frontline healthcare workers and healthcare workers stationed at the point-of-entry services (emergency and outpatient clinics) had a high rate of infections. However, previous SARS-CoV-2 infections (HR\u2009=\u20090.80, 95% CI: 0.71\u20130.53) and full vaccination (HR\u2009=\u20090.56, 95% CI: 0.51\u20130.62) conferred some protection, despite an overall rise in infection post vaccination incidence.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec004\">\n<jats:title>Conclusion<\/jats:title>\n<jats:p>In conclusion, the results of our study suggest a high incidence of post-vaccination infections among healthcare workers in the context of varying epidemic waves. Additionally, the study identified partial or incomplete vaccination, elderly workers, comorbidities, frontline workers, nurses and point-of-entry service roles as high-risk factors for post-vaccination infections. These findings reinforce the need for tailored booster strategies and strengthened protection for high-risk healthcare workers in LMIC settings.<\/jats:p>\n<\/jats:sec>","DOI":"10.1371\/journal.pone.0331971","type":"journal-article","created":{"date-parts":[[2025,9,17]],"date-time":"2025-09-17T17:29:22Z","timestamp":1758130162000},"page":"e0331971","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":1,"title":["Post-vaccination SARS-CoV-2 infections among healthcare workers in a tertiary hospital in Ghana"],"prefix":"10.1371","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6318-9937","authenticated-orcid":true,"given":"Kissinger","family":"Marfoh","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ali","family":"Samba","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Eunice","family":"Okyere","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ahmad Zaid","family":"Fattah","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dorothy Naa Ashokor","family":"Darko","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Prince Nuertey","family":"Odoom","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-4620-0197","authenticated-orcid":true,"given":"Michael Darko","family":"Ashaley","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"340","published-online":{"date-parts":[[2025,9,17]]},"reference":[{"issue":"1","key":"pone.0331971.ref001","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1186\/s41182-023-00564-2","article-title":"Vaccine inequity: a threat to Africa\u2019s recovery from COVID-19","volume":"51","author":"CR Wei","year":"2023","journal-title":"Trop Med Health"},{"key":"pone.0331971.ref002","doi-asserted-by":"crossref","DOI":"10.1007\/s00281-023-00998-0","article-title":"Causes and costs of global COVID-19 vaccine inequity","volume-title":"Seminars in Immunopathology","author":"M Ferranna","year":"2024"},{"key":"pone.0331971.ref003","unstructured":"World Health Organization. COVID-19 vaccination 2025. n.d. https:\/\/data.who.int\/dashboards\/covid19\/vaccines"},{"issue":"1","key":"pone.0331971.ref004","doi-asserted-by":"crossref","first-page":"577","DOI":"10.1186\/s12879-023-08553-w","article-title":"SARS-CoV-2 vaccine breakthrough infection in the older adults: a meta-analysis and systematic review","volume":"23","author":"X Jing","year":"2023","journal-title":"BMC Infect Dis"},{"issue":"1","key":"pone.0331971.ref005","doi-asserted-by":"crossref","first-page":"1003","DOI":"10.1186\/s12879-024-09902-z","article-title":"COVID-19 breakthrough infections in vaccinated individuals at BPKIHS, Nepal","volume":"24","author":"A Karmacharya","year":"2024","journal-title":"BMC Infect Dis"},{"issue":"8","key":"pone.0331971.ref006","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pone.0302338","article-title":"Incidence and risk factors of SARS-CoV-2 breakthrough infection in the early Omicron variant era among vaccinated and boosted individuals in Chicago","volume":"19","author":"F Moreno Echevarria","year":"2024","journal-title":"PLoS One"},{"issue":"10","key":"pone.0331971.ref007","doi-asserted-by":"crossref","first-page":"1164","DOI":"10.1093\/infdis\/jiad020","article-title":"Incidence and Predictors of Breakthrough and Severe Breakthrough Infections of SARS-CoV-2 After Primary Series Vaccination in Adults: A Population-Based Survey of 22 575 Participants","volume":"227","author":"SM DeSantis","year":"2023","journal-title":"J Infect Dis"},{"issue":"1","key":"pone.0331971.ref008","doi-asserted-by":"crossref","first-page":"202","DOI":"10.1038\/s41392-022-01039-2","article-title":"Molecular characteristics, immune evasion, and impact of SARS-CoV-2 variants","volume":"7","author":"C Sun","year":"2022","journal-title":"Signal Transduct Target Ther"},{"issue":"21","key":"pone.0331971.ref009","doi-asserted-by":"crossref","first-page":"792","DOI":"10.15585\/mmwr.mm7021e3","article-title":"COVID-19 Vaccine Breakthrough Infections Reported to CDC - United States, January 1-April 30, 2021","volume":"70","author":"CDC COVID-19 Vaccine Breakthrough Case Investigations Team","year":"2021","journal-title":"MMWR Morb Mortal Wkly Rep"},{"issue":"10321","key":"pone.0331971.ref010","doi-asserted-by":"crossref","first-page":"234","DOI":"10.1016\/S0140-6736(21)02844-0","article-title":"Reduced neutralisation of SARS-CoV-2 omicron B.1.1.529 variant by post-immunisation serum","volume":"399","author":"W Dejnirattisai","year":"2022","journal-title":"Lancet"},{"issue":"2","key":"pone.0331971.ref011","doi-asserted-by":"crossref","first-page":"2271089","DOI":"10.1080\/22221751.2023.2271089","article-title":"Less neutralization evasion of SARS-CoV-2 BA.2.86 than XBB sublineages and CH.1.1","volume":"12","author":"Y Hu","year":"2023","journal-title":"Emerg Microbes Infect"},{"issue":"2","key":"pone.0331971.ref012","doi-asserted-by":"crossref","first-page":"358","DOI":"10.1038\/s41591-022-02138-x","article-title":"Infectiousness of SARS-CoV-2 breakthrough infections and reinfections during the Omicron wave","volume":"29","author":"ST Tan","year":"2023","journal-title":"Nat Med"},{"issue":"10269","key":"pone.0331971.ref013","doi-asserted-by":"crossref","first-page":"99","DOI":"10.1016\/S0140-6736(20)32661-1","article-title":"Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK","volume":"397","author":"M Voysey","year":"2021","journal-title":"The Lancet"},{"key":"pone.0331971.ref014","article-title":"Clinical severity of, and effectiveness of mRNA vaccines against, covid-19 from omicron, delta, and alpha SARS-CoV-2 variants in the United States: prospective observational study","volume":"376","author":"AS Lauring","year":"2022","journal-title":"BMJ"},{"issue":"2","key":"pone.0331971.ref015","article-title":"Estimation of Vaccine Effectiveness of CoronaVac and BNT162b2 Against Severe Outcomes Over Time Among Patients With SARS-CoV-2 Omicron","volume":"6","author":"Y Wei","year":"2023","journal-title":"JAMA Netw Open"},{"issue":"16","key":"pone.0331971.ref016","doi-asserted-by":"crossref","first-page":"1532","DOI":"10.1056\/NEJMoa2119451","article-title":"Covid-19 vaccine effectiveness against the Omicron (B. 1.1. 529) variant","volume":"386","author":"N Andrews","year":"2022","journal-title":"New England Journal of Medicine"},{"issue":"1","key":"pone.0331971.ref017","doi-asserted-by":"crossref","first-page":"2300703","DOI":"10.2807\/1560-7917.ES.2024.29.1.2300703","article-title":"Early COVID-19 vaccine effectiveness of XBB.1.5 vaccine against hospitalisation and admission to intensive care, the Netherlands, 9 October to 5 December 2023","volume":"29","author":"CH van Werkhoven","year":"2024","journal-title":"Euro Surveill"},{"issue":"1","key":"pone.0331971.ref018","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1080\/14760584.2023.2143347","article-title":"Expert review of global real-world data on COVID-19 vaccine booster effectiveness and safety during the omicron-dominant phase of the pandemic","volume":"22","author":"R Solante","year":"2023","journal-title":"Expert Rev Vaccines"},{"issue":"6","key":"pone.0331971.ref019","doi-asserted-by":"crossref","first-page":"843","DOI":"10.1016\/j.jiph.2020.05.019","article-title":"SARS, MERS and COVID-19 among healthcare workers: A narrative review","volume":"13","author":"J Xiao","year":"2020","journal-title":"J Infect Public Health"},{"issue":"1","key":"pone.0331971.ref020","doi-asserted-by":"crossref","first-page":"46","DOI":"10.1186\/s13756-023-01247-7","article-title":"Combining epidemiological data and whole genome sequencing to understand SARS-CoV-2 transmission dynamics in a large tertiary care hospital during the first COVID-19 wave in The Netherlands focusing on healthcare workers","volume":"12","author":"CP Haanappel","year":"2023","journal-title":"Antimicrob Resist Infect Control"},{"issue":"12","key":"pone.0331971.ref021","doi-asserted-by":"crossref","first-page":"1100","DOI":"10.1016\/j.it.2020.10.004","article-title":"Mechanisms of SARS-CoV-2 Transmission and Pathogenesis","volume":"41","author":"AG Harrison","year":"2020","journal-title":"Trends Immunol"},{"issue":"2","key":"pone.0331971.ref022","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pone.0247163","article-title":"Role of ivermectin in the prevention of SARS-CoV-2 infection among healthcare workers in India: A matched case-control study","volume":"16","author":"P Behera","year":"2021","journal-title":"PLoS One"},{"issue":"12","key":"pone.0331971.ref023","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pone.0260453","article-title":"Potential SARS-CoV-2 infectiousness among asymptomatic healthcare workers","volume":"16","author":"VN Pimenoff","year":"2021","journal-title":"PLoS One"},{"issue":"7985","key":"pone.0331971.ref024","doi-asserted-by":"crossref","first-page":"132","DOI":"10.1038\/s41586-023-06634-z","article-title":"The burden and dynamics of hospital-acquired SARS-CoV-2 in England","volume":"623","author":"BS Cooper","year":"2023","journal-title":"Nature"},{"issue":"10","key":"pone.0331971.ref025","article-title":"Transmission of community- and hospital-acquired SARS-CoV-2 in hospital settings in the UK: A cohort study","volume":"18","author":"Y Mo","year":"2021","journal-title":"PLoS Med"},{"issue":"1","key":"pone.0331971.ref026","doi-asserted-by":"crossref","first-page":"4705","DOI":"10.1038\/s41598-025-89472-5","article-title":"SARS-CoV-2 infection rates and associated risk factors in healthcare workers: systematic review and meta-analysis","volume":"15","author":"A Bansal","year":"2025","journal-title":"Sci Rep"},{"issue":"4","key":"pone.0331971.ref027","doi-asserted-by":"crossref","first-page":"505","DOI":"10.1093\/heapol\/czab133","article-title":"Seroprevalence and risk factors of COVID-19 in healthcare workers from 11 African countries: a scoping review and appraisal of existing evidence","volume":"37","author":"SA M\u00fcller","year":"2022","journal-title":"Health Policy Plan"},{"key":"pone.0331971.ref028","unstructured":"World Health Organization. WHO coronavirus disease (COVID-19) dashboard. 2023. https:\/\/covid19.who.int\/"},{"issue":"4","key":"pone.0331971.ref029","doi-asserted-by":"crossref","first-page":"1220","DOI":"10.3201\/eid2704.210016","article-title":"Postvaccination COVID-19 among healthcare workers, Israel","volume":"27","author":"S Amit","year":"2021","journal-title":"Emerging Infectious Diseases"},{"key":"pone.0331971.ref030","unstructured":"World Health Organization. COVID-19 vaccine coverage, World 2025. https:\/\/data.who.int\/dashboards\/covid19\/vaccines?n=o"},{"key":"pone.0331971.ref031","unstructured":"Ghana Health Service. COVID-19 vaccines doses administration. n.d. https:\/\/www.ghs.gov.gh\/covid19\/"},{"key":"pone.0331971.ref032","doi-asserted-by":"crossref","first-page":"103208","DOI":"10.1016\/j.jbi.2019.103208","article-title":"The REDCap consortium: Building an international community of software platform partners","volume":"95","author":"PA Harris","year":"2019","journal-title":"J Biomed Inform"},{"issue":"2","key":"pone.0331971.ref033","doi-asserted-by":"crossref","first-page":"377","DOI":"10.1016\/j.jbi.2008.08.010","article-title":"Research electronic data capture (REDCap)--a metadata-driven methodology and workflow process for providing translational research informatics support","volume":"42","author":"PA Harris","year":"2009","journal-title":"J Biomed Inform"},{"issue":"6","key":"pone.0331971.ref034","doi-asserted-by":"crossref","DOI":"10.1136\/bmjopen-2022-061643","article-title":"Adverse events following immunisation (AEFI) of COVISHIELD vaccination among healthcare workers in Ghana","volume":"13","author":"K Marfoh","year":"2023","journal-title":"BMJ Open"},{"issue":"4","key":"pone.0331971.ref035","doi-asserted-by":"crossref","first-page":"115628","DOI":"10.1016\/j.diagmicrobio.2021.115628","article-title":"Evaluation of the Roche-SD Biosensor rapid antigen test: Antigen is not reliable in detecting SARS-CoV-2 at the early stage of infection with respiratory symptoms","volume":"102","author":"H Flinck","year":"2022","journal-title":"Diagn Microbiol Infect Dis"},{"key":"pone.0331971.ref036","article-title":"Clinical performance of SARS-CoV-2 rapid antigen tests: a systematic review and meta-analysis","author":"N Germic","year":"2023","journal-title":"medRxiv"},{"key":"pone.0331971.ref037","volume-title":"R: A Language and Environment for Statistical Computing","author":"Team RC","year":"2021"},{"issue":"5","key":"pone.0331971.ref038","doi-asserted-by":"crossref","first-page":"766","DOI":"10.1016\/j.ajo.2008.07.042","article-title":"Logistic regression analysis: applications to ophthalmic research","volume":"147","author":"S Lemeshow","year":"2009","journal-title":"Am J Ophthalmol"},{"key":"pone.0331971.ref039","doi-asserted-by":"crossref","first-page":"212","DOI":"10.1016\/S0140-6736(21)00947-8","article-title":"Impact and effectiveness of mRNA BNT162b2 vaccine against SARS-CoV-2 infections and COVID-19 cases, hospitalisations, and deaths following a nationwide vaccination campaign in Israel: an observational study using national surveillance data","volume":"397","author":"E Haas","year":"2021","journal-title":"Lancet"},{"issue":"7","key":"pone.0331971.ref040","doi-asserted-by":"crossref","DOI":"10.1016\/j.jval.2022.04.891","article-title":"EPH140 SARS-COV-2 Breakthrough Infections Among the Healthcare Workers Post-Vaccination with ChAdOx1 nCoV-19 Vaccine in the South Indian State of Kerala","volume":"25","author":"A Issac","year":"2022","journal-title":"Value in Health"},{"issue":"4","key":"pone.0331971.ref041","doi-asserted-by":"crossref","first-page":"596","DOI":"10.1016\/j.cmi.2021.11.023","article-title":"Postvaccination infections among staff of a tertiary care hospital after vaccination with severe acute respiratory syndrome coronavirus 2 vector and mRNA-based vaccines","volume":"28","author":"S Brunner-Ziegler","year":"2022","journal-title":"Clin Microbiol Infect"},{"issue":"3","key":"pone.0331971.ref042","first-page":"34218","article-title":"COVID-19 Vaccine Hesitancy Among Healthcare Providers","volume":"10","author":"D Huang","year":"2022","journal-title":"Health Psychol Res"},{"issue":"31","key":"pone.0331971.ref043","doi-asserted-by":"crossref","first-page":"4081","DOI":"10.1016\/j.vaccine.2022.04.097","article-title":"Factors affecting COVID-19 vaccine hesitancy among healthcare providers in 23 countries","volume":"40","author":"JP Leigh","year":"2022","journal-title":"Vaccine"},{"key":"pone.0331971.ref044","doi-asserted-by":"crossref","first-page":"1046546","DOI":"10.3389\/fpubh.2022.1046546","article-title":"Is heterologous prime-boost COVID-19 vaccination a concern or an opportunity for Ethiopia?","volume":"10","author":"T Gelanew","year":"2023","journal-title":"Front Public Health"},{"issue":"11","key":"pone.0331971.ref045","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pgph.0002639","article-title":"Examining the uptake of COVID-19 vaccine booster doses among healthcare workers in South Africa: A mixed-methods study","volume":"3","author":"G George","year":"2023","journal-title":"PLOS Glob Public Health"},{"issue":"4","key":"pone.0331971.ref046","doi-asserted-by":"crossref","DOI":"10.1136\/bmjgh-2022-009010","article-title":"COVID-19 vaccine wastage in the midst of vaccine inequity: causes, types and practical steps","volume":"7","author":"JV Lazarus","year":"2022","journal-title":"BMJ Glob Health"},{"issue":"1","key":"pone.0331971.ref047","doi-asserted-by":"crossref","DOI":"10.1136\/bmjgh-2023-013680","article-title":"Lessons learnt from COVID-19 to reduce mortality and morbidity in the Global South: addressing global vaccine equity for future pandemics","volume":"9","author":"R Martin","year":"2024","journal-title":"BMJ Glob Health"},{"key":"pone.0331971.ref048","unstructured":"Ghana Health Service begins covid booster vaccination. 2022. https:\/\/www.gbcghanaonline.com\/news\/health\/231930\/2022\/?utm_source=chatgpt.com"},{"issue":"6","key":"pone.0331971.ref049","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pone.0305993","article-title":"COVID-19 vaccine acceptance and hesitancy in Ghana: A systematic review","volume":"19","author":"GB Akrong","year":"2024","journal-title":"PLoS One"},{"issue":"1","key":"pone.0331971.ref050","doi-asserted-by":"crossref","first-page":"2673","DOI":"10.1186\/s12889-024-20201-9","article-title":"Acceptance of COVID-19 vaccine booster doses among the Adult Population in Ghana: a cross-sectional study using the Health Belief Model","volume":"24","author":"G Eshun","year":"2024","journal-title":"BMC Public Health"},{"key":"pone.0331971.ref051","unstructured":"Gyesi ZK. Ghana Health Service rolls out nationwide COVID-19 vaccination campaign. 2024. https:\/\/www.graphic.com.gh\/news\/general-news\/ghana-health-service-rolls-out-nationwide-covid-19-vaccination-campaign.html"},{"key":"pone.0331971.ref052","unstructured":"Ghanaweb. COVID 19 Resurgence - Government initiates moves to secure vaccines - Health minister. 2025. https:\/\/www.ghanaweb.com\/GhanaHomePage\/NewsArchive\/COVID-19-Resurgence-Government-initiates-moves-to-secure-vaccines-Health-minister-1989984"},{"key":"pone.0331971.ref053","doi-asserted-by":"crossref","first-page":"100109","DOI":"10.1016\/j.clinsp.2022.100109","article-title":"COVID-19 post-vaccination in healthcare workers and vaccine effectiveness, Brazil, 2021","volume":"77","author":"CM Fernandes","year":"2022","journal-title":"Clinics (Sao Paulo)"},{"issue":"1","key":"pone.0331971.ref054","doi-asserted-by":"crossref","first-page":"10","DOI":"10.1016\/j.jiph.2021.11.015","article-title":"Post-vaccination SARS-CoV-2 infection among healthcare workers in tertiary care hospitals in Saudi Arabia: A case series","volume":"15","author":"MM Alshamrani","year":"2022","journal-title":"J Infect Public Health"},{"issue":"1","key":"pone.0331971.ref055","doi-asserted-by":"crossref","DOI":"10.1186\/s43168-023-00244-z","article-title":"COVID-19 Post- vaccination infection among hospital attendants in Qena city","volume":"17","author":"RA Mohamed","year":"2023","journal-title":"Egypt J Bronchol"},{"issue":"8","key":"pone.0331971.ref056","doi-asserted-by":"crossref","DOI":"10.1001\/jamanetworkopen.2023.29441","article-title":"Assessment of hospital-onset SARS-CoV-2 infection rates and testing practices in the US, 2020-2022","volume":"6","author":"KM Hatfield","year":"2023","journal-title":"JAMA Network Open"},{"key":"pone.0331971.ref057","unstructured":"CDC. Operational considerations for infection prevention and control in outpatient facilities: non-U.S. healthcare settings. 2024. https:\/\/www.cdc.gov\/covid\/hcp\/non-us-settings\/outpatient.html?utm_source=chatgpt.com"},{"key":"pone.0331971.ref058","doi-asserted-by":"crossref","first-page":"104710","DOI":"10.1016\/j.jcv.2020.104710","article-title":"SARS-CoV-2 infection among asymptomatic healthcare workers of the emergency department in a tertiary care facility","volume":"134","author":"R Abdelmoniem","year":"2021","journal-title":"J Clin Virol"},{"key":"pone.0331971.ref059","doi-asserted-by":"crossref","DOI":"10.1093\/occmed\/kqaa036","volume-title":"Occupational risks for COVID-19 infection","author":"D Koh","year":"2020"},{"issue":"1","key":"pone.0331971.ref060","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1186\/s12985-023-02018-x","article-title":"A comparison of transmissibility of SARS-CoV-2 variants of concern","volume":"20","author":"SS Manathunga","year":"2023","journal-title":"Virol J"},{"key":"pone.0331971.ref061","doi-asserted-by":"crossref","first-page":"898101","DOI":"10.3389\/fmed.2022.898101","article-title":"Association Between Vaccination Coverage Disparity and the Dynamics of the COVID-19 Delta and Omicron Waves in the US","volume":"9","author":"DF Cuadros","year":"2022","journal-title":"Front Med (Lausanne)"},{"issue":"7","key":"pone.0331971.ref062","doi-asserted-by":"crossref","DOI":"10.1136\/bmjgh-2023-012328","article-title":"Severity and outcomes of Omicron variant of SARS-CoV-2 compared to Delta variant and severity of Omicron sublineages: a systematic review and metanalysis","volume":"8","author":"P Relan","year":"2023","journal-title":"BMJ Glob Health"},{"issue":"1","key":"pone.0331971.ref063","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/s12879-023-08748-1","article-title":"Assessing the COVID-19 vaccination program during the Omicron variant (B. 1.1. 529) epidemic in early 2022, Tokyo","volume":"23","author":"T Kayano","year":"2023","journal-title":"BMC Infectious Diseases"},{"issue":"1","key":"pone.0331971.ref064","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1016\/S1473-3099(21)00460-6","article-title":"Risk factors and disease profile of post-vaccination SARS-CoV-2 infection in UK users of the COVID Symptom Study app: a prospective, community-based, nested, case-control study","volume":"22","author":"M Antonelli","year":"2022","journal-title":"Lancet Infect Dis"},{"key":"pone.0331971.ref065","article-title":"Rate and risk factors for severe\/critical disease among fully vaccinated persons with breakthrough SARS-CoV-2 infection in a high-risk national population","author":"AA Butt","year":"2021","journal-title":"Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America"},{"key":"pone.0331971.ref066","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1186\/s12979-019-0164-9","article-title":"Immunosenescence and human vaccine immune responses","volume":"16","author":"SN Crooke","year":"2019","journal-title":"Immun Ageing"},{"issue":"7","key":"pone.0331971.ref067","doi-asserted-by":"crossref","first-page":"1078","DOI":"10.1086\/529197","article-title":"Biology of immune responses to vaccines in elderly persons","volume":"46","author":"B Weinberger","year":"2008","journal-title":"Clin Infect Dis"},{"issue":"1","key":"pone.0331971.ref068","doi-asserted-by":"crossref","first-page":"58","DOI":"10.1038\/s43856-023-00277-x","article-title":"Impact of age and comorbidities on SARS-CoV-2 vaccine-induced T cell immunity","volume":"3","author":"LL Dietz","year":"2023","journal-title":"Commun Med (Lond)"},{"issue":"48","key":"pone.0331971.ref069","doi-asserted-by":"crossref","first-page":"2000895","DOI":"10.2807\/1560-7917.ES.2020.25.48.2000895","article-title":"Clinical characteristics and risk factors associated with severe COVID-19: prospective analysis of 1,045 hospitalised cases in North-Eastern France, March 2020","volume":"25","author":"C Kaeuffer","year":"2020","journal-title":"Euro Surveill"},{"key":"pone.0331971.ref070","article-title":"The SARS-CoV-2 mRNA vaccine breakthrough infection phenotype includes significant symptoms, live virus shedding, and viral genetic diversity","author":"SD Pollett","year":"2021","journal-title":"Clin Infect Dis"},{"key":"pone.0331971.ref071","doi-asserted-by":"crossref","DOI":"10.15585\/mmwr.mm7017e1","article-title":"Postvaccination SARS-CoV-2 infections among skilled nursing facility residents and staff members\u2014Chicago, Illinois, December 2020\u2013March 2021","volume":"70","author":"RA Teran","year":"2021","journal-title":"MMWR Morbidity and Mortality Weekly Report"},{"key":"pone.0331971.ref072","article-title":"A retrospective analysis of COVID-19 mRNA vaccine breakthrough infections\u2013risk factors and vaccine effectiveness","author":"C Liu","year":"2021","journal-title":"medRxiv"},{"issue":"1","key":"pone.0331971.ref073","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pone.0245556","article-title":"Sex differences in susceptibility, severity, and outcomes of coronavirus disease 2019: Cross-sectional analysis from a diverse US metropolitan area","volume":"16","author":"FS Vahidy","year":"2021","journal-title":"PLoS One"},{"issue":"6","key":"pone.0331971.ref074","doi-asserted-by":"crossref","first-page":"102306","DOI":"10.1016\/j.dsx.2021.102306","article-title":"Symptomatic post-vaccination SARS-CoV-2 infections in healthcare workers- A multicenter cohort study","volume":"15","author":"R Vaishya","year":"2021","journal-title":"Diabetes Metab Syndr"},{"issue":"1","key":"pone.0331971.ref075","doi-asserted-by":"crossref","DOI":"10.1093\/cid\/ciab1038","article-title":"Neutralizing Antibody Response to Pseudotype Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Differs Between mRNA-1273 and BNT162b2 Coronavirus Disease 2019 (COVID-19) Vaccines and by History of SARS-CoV-2 Infection","volume":"75","author":"HL Tyner","year":"2022","journal-title":"Clin Infect Dis"},{"issue":"1","key":"pone.0331971.ref076","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1186\/s13293-020-00330-7","article-title":"Sex differences in severity and mortality from COVID-19: are males more vulnerable?","volume":"11","author":"A Pradhan","year":"2020","journal-title":"Biol Sex Differ"},{"key":"pone.0331971.ref077","article-title":"Effectiveness of mRNA vaccines and waning of protection against SARS-CoV-2 infection and severe covid-19 during predominant circulation of the delta variant in Italy: retrospective cohort study","volume":"376","author":"M Fabiani","year":"2022","journal-title":"BMJ"},{"issue":"10292","key":"pone.0331971.ref078","doi-asserted-by":"crossref","first-page":"2331","DOI":"10.1016\/S0140-6736(21)01290-3","article-title":"Neutralising antibody activity against SARS-CoV-2 VOCs B. 1.617. 2 and B. 1.351 by BNT162b2 vaccination","volume":"397","author":"EC Wall","year":"2021","journal-title":"The Lancet"},{"issue":"6","key":"pone.0331971.ref079","doi-asserted-by":"crossref","first-page":"557","DOI":"10.1016\/S2213-2600(22)00042-X","article-title":"Comparative vaccine effectiveness against severe COVID-19 over time in US hospital administrative data: a case-control study","volume":"10","author":"BJ Wright","year":"2022","journal-title":"Lancet Respir Med"}],"container-title":["PLOS One"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0331971","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,9,17]],"date-time":"2025-09-17T17:29:39Z","timestamp":1758130179000},"score":1,"resource":{"primary":{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0331971"}},"subtitle":[],"editor":[{"given":"Krit","family":"Pongpirul","sequence":"first","affiliation":[],"role":[{"role":"editor","vocabulary":"crossref"}]}],"short-title":[],"issued":{"date-parts":[[2025,9,17]]},"references-count":79,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2025,9,17]]}},"URL":"https:\/\/doi.org\/10.1371\/journal.pone.0331971","relation":{},"ISSN":["1932-6203"],"issn-type":[{"value":"1932-6203","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,9,17]]}}}