Hoeve, Christel ENeppelenbroek, NienkeVos, Eric R AHuiberts, Anne JAndeweg, Stijn Pden Hartog, Gercovan Binnendijk, Robertde Melker, Hestervan den Hof, SusanKnol, Mirjam2025-03-042025-03-042025-02-071469-44093991526710.1017/S095026882500010Xhttps://rivm.openrepository.com/handle/10029/628419We assessed the validity of serum total anti-nucleoprotein Immunoglobulin (-antibodies) to identify SARS-CoV-2 (re)infections by estimating the persistence of -antibody seropositivity and boosting following infection. From a prospective Dutch cohort study (VASCO), we included adult participants with ≥2 consecutive self-collected serum samples, 4-8 months apart, between May 2021-May 2023. Sample pairs were stratified by -seropositivity of the first sample and by self-reported infection within the sampling interval. We calculated the proportions of participants with -seroconversion and fold-increase (1.5, 2, 3, 4) of -antibody concentration over time since infection and explored determinants. We included 67,632 sample pairs. Pairs with a seronegative first sample (70%) showed 89% -seroconversion after reported infection and 11% when no infection was reported. In pairs with a seropositive first sample (30%), 82%-65% showed a 1.5- to 4-fold increase with a reported reinfection, and 19%-10% without a reported reinfection, respectively. After one year, 83% remained -seropositive post-first infection and 93%-61% showed a 1.5-fold to 4-fold increase post-reinfection. Odds for seroconversion/fold increase were higher for symptomatic infections and Omicron infections. In the current era with limited antigen or PCR testing, -serology can be validly used to detect SARS-CoV-2 (re)infections at least up to a year after infection, supporting the monitoring of COVID-19 burden and vaccine effectiveness.enSARS-CoV-2antibodycohort studyinfectionnucleoproteinprospectiveJournal ArticleEpidemiol Infect 2025;153:e38S095026882500010X