{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,12]],"date-time":"2026-01-12T21:22:44Z","timestamp":1768252964293,"version":"3.49.0"},"reference-count":41,"publisher":"Public Library of Science (PLoS)","issue":"8","license":[{"start":{"date-parts":[[2022,8,24]],"date-time":"2022-08-24T00:00:00Z","timestamp":1661299200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Provost\u2019s Academic Priorities Fund, The Aga Khan University"}],"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>An estimated 1.5 million cases were reported in Pakistan until 23 March, 2022. However, SARS-CoV-2 PCR testing capacity has been limited and the incidence of COVID-19 infections is unknown. Volunteer healthy blood donors can be a control population for assessment of SARS-CoV-2 exposure in the population. We determined COVID-19 seroprevalence during the second pandemic wave in Karachi in donors without known infections or symptoms in 4 weeks prior to enrollment.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec002\">\n<jats:title>Materials and methods<\/jats:title>\n<jats:p>We enrolled 558 healthy blood donors at the Aga Khan University Hospital between December 2020 and February 2021. ABO blood groups were determined. Serum IgG reactivity were measured to spike and receptor binding domain (RBD) proteins.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec003\">\n<jats:title>Results<\/jats:title>\n<jats:p>Study subjects were predominantly males (99.1%) with a mean age of 29.0\u00b17.4 years. Blood groups were represented by; B (35.8%), O (33.3%), A (23.8%) and AB (7%). Positive IgG responses to spike were detected in 53.4% (95% CI, 49.3\u201337.5) of blood donors. Positive IgG antibodies to RBD were present in 16.7% (95% CI; 13.6\u201319.8) of individuals. No significant difference was found between the frequency of IgG antibodies to spike or RBD across age groups. Frequencies of IgG to Spike and RBD antibodies between December 2020 and February 2021 were found to be similar. Seropositivity to either antigen between individuals of different blood groups did not differ. Notably, 31.2% of individuals with IgG antibodies to spike also had IgG antibodies to RBD. Amongst donors who had previously confirmed COVID-19 and were seropositive to spike, 40% had IgG to RBD.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec004\">\n<jats:title>Conclusions<\/jats:title>\n<jats:p>Our study provides insights into the seroprevalence of antibodies to COVID-19 in a healthy cohort in Karachi. The differential dynamics of IgG to spike and RBD likely represent both exposure to SARS-CoV-2 and associate with protective immunity in the population.<\/jats:p>\n<\/jats:sec>","DOI":"10.1371\/journal.pone.0271259","type":"journal-article","created":{"date-parts":[[2022,8,24]],"date-time":"2022-08-24T17:35:44Z","timestamp":1661362544000},"page":"e0271259","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":17,"title":["IgG antibodies to SARS-CoV-2 in asymptomatic blood donors at two time points in Karachi"],"prefix":"10.1371","volume":"17","author":[{"given":"Muhammad","family":"Hasan","sequence":"first","affiliation":[]},{"given":"Bushra","family":"Moiz","sequence":"additional","affiliation":[]},{"given":"Shama","family":"Qaiser","sequence":"additional","affiliation":[]},{"given":"Kiran Iqbal","family":"Masood","sequence":"additional","affiliation":[]},{"given":"Zara","family":"Ghous","sequence":"additional","affiliation":[]},{"given":"Areeba","family":"Hussain","sequence":"additional","affiliation":[]},{"given":"Natasha","family":"Ali","sequence":"additional","affiliation":[]},{"given":"J. Pedro","family":"Simas","sequence":"additional","affiliation":[]},{"given":"Marc","family":"Veldhoen","sequence":"additional","affiliation":[]},{"given":"Paula","family":"Alves","sequence":"additional","affiliation":[]},{"given":"Syed Hani","family":"Abidi","sequence":"additional","affiliation":[]},{"given":"Kulsoom","family":"Ghias","sequence":"additional","affiliation":[]},{"given":"Erum","family":"Khan","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7580-372X","authenticated-orcid":true,"given":"Zahra","family":"Hasan","sequence":"additional","affiliation":[]}],"member":"340","published-online":{"date-parts":[[2022,8,24]]},"reference":[{"issue":"18","key":"pone.0271259.ref001","doi-asserted-by":"crossref","first-page":"1708","DOI":"10.1056\/NEJMoa2002032","article-title":"Clinical Characteristics of Coronavirus Disease 2019 in China","volume":"382","author":"WJ Guan","year":"2020","journal-title":"N Engl J Med"},{"issue":"10223","key":"pone.0271259.ref002","doi-asserted-by":"crossref","first-page":"497","DOI":"10.1016\/S0140-6736(20)30183-5","article-title":"Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China","volume":"395","author":"C Huang","year":"2020","journal-title":"Lancet"},{"key":"pone.0271259.ref003","article-title":"COVID-19 Health Advisory Platform","author":"Pakistan Go","year":"2021","journal-title":"Ministry of National Health Services Regulations and Coordination"},{"issue":"9","key":"pone.0271259.ref004","doi-asserted-by":"crossref","first-page":"891","DOI":"10.1111\/resp.14093","article-title":"COVID-19 situation in Pakistan: A broad overview","volume":"26","author":"M Imran","year":"2021","journal-title":"Respirology"},{"key":"pone.0271259.ref005","author":"JHU","year":"2021","journal-title":"Coronavirus Resource Center: John Hopkins University of Medicine"},{"key":"pone.0271259.ref006","unstructured":"GoS. Daily Situation Report 2021 [Available from: https:\/\/www.sindhhealth.gov.pk\/upload\/daily_status_report\/Daily_Situation_Report_for_1st_January_2021.pdf"},{"key":"pone.0271259.ref007","doi-asserted-by":"crossref","first-page":"285","DOI":"10.1016\/j.ijid.2020.10.091","article-title":"The prevalence of asymptomatic and symptomatic COVID-19 in a cohort of quarantined subjects","volume":"102","author":"M Al-Qahtani","year":"2021","journal-title":"International Journal of Infectious Diseases"},{"key":"pone.0271259.ref008","author":"A. 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