{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T19:14:22Z","timestamp":1772133262344,"version":"3.50.1"},"reference-count":40,"publisher":"Public Library of Science (PLoS)","issue":"2","license":[{"start":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T00:00:00Z","timestamp":1772064000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/"}],"funder":[{"DOI":"10.13039\/100006492","name":"Division of Intramural Research, National Institute of Allergy and Infectious Diseases","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100006492","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosglobalpublichealth.org"],"crossmark-restriction":false},"short-container-title":["PLOS Glob Public Health"],"abstract":"<jats:p>COVID-19 was first reported in the Philippines in January 2020 and the country experienced several COVID-19 waves. Little is known on the seroprevalence of SARS-CoV-2 among adolescents in a developing country such as the Philippines. In this study, we incorporated testing for acute COVID-19 and SARS-CoV-2 seropositivity in an ongoing dengue study of 9- to 14-year-old participants enrolled in 2017. Acute febrile episodes were detected through active surveillance and a nasopharyngeal swab was obtained for SARS-CoV-2 RT-PCR. Before COVID-19 vaccination was offered, we tested a subset of sera obtained in 2021 for SARS-CoV-2 receptor binding domain (RBD) antibodies. Development of SARS-CoV-2 seropositivity acquired through natural infection and vaccination was conducted by measuring antibodies pre- (2018\u20132019), early- (2019\u20132020), and late-pandemic (2022\u20132023) in those with matched samples. From July 2021-October 2022, we recorded 29 acute febrile illness episodes in the cohort and 17.0% were SARS-CoV-2 RT-PCR positive. In the subset of 499 samples tested for SARS-CoV-2 RBD antibodies in 2021, 30.3% were seropositive. Among these, 4.0% were seropositive in 2018\u20132019, and 11.0% had seroconverted by 2020. Interestingly, 74.0% experienced antibody waning between 2020 and 2021 sampling. By 2022, 345\/499 children received full COVID-19 vaccination and 13\/499 was partially vaccinated, with 96.6% SARS-CoV-2 seropositive by late-pandemic sample in 2022\u20132023. Vaccination and site were predictors of SARS-CoV-2 RBD antibodies. These findings suggest both variation in local transmission over time as well as association of vaccination with the development of SARS-CoV-2 immunity in adolescents in the Philippines.<\/jats:p>","DOI":"10.1371\/journal.pgph.0005961","type":"journal-article","created":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T18:32:58Z","timestamp":1772130778000},"page":"e0005961","update-policy":"https:\/\/doi.org\/10.1371\/journal.pgph.corrections_policy","source":"Crossref","is-referenced-by-count":0,"title":["Development of seropositivity to SARS-CoV-2 over the course of the COVID-19 pandemic in adolescents in a longitudinal cohort study in Cebu, Philippines"],"prefix":"10.1371","volume":"6","author":[{"given":"Jedas Veronica","family":"Daag","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Gianne Lariz","family":"Magsakay","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7140-8845","authenticated-orcid":true,"given":"Silvia Blanco","family":"Rivera","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ma. 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