Even considering that we may be overestimating the seroprevalence,13 it is reasonable to expect that this SARS-CoV-2 infection was considerably more frequent than based on notified cases as shown previously,14 particularly because testing was restricted during the initial phase of the epidemic. No workers with an isolated IgM reactive result had a positive RT-PCR, supporting the evidence that when antibodies start being detectable the computer virus detection by RT-PCR is lower, and that antibody assessments are appropriate to identify those previously infected but not to detect active infections.2 Nevertheless, we cannot rule out the hypothesis of false-positive IgM results due to lower specificity.15 Importantly, the test results were read by the trained field researchers who performed it and in case of doubt there was always an experienced field supervisor to be consulted. As we had to use two different assessments, though from the same manufacturer and with similar performance characteristics, error in the prevalence estimate could have occurred. to 4.3%) for IgM, 0.6% (95% CrI 0.0% to 1 1.3%) for IgG, and 2.5% (95% CrI 0.1% to 5.3%) for IgM or IgG. A SARS-CoV-2 molecular diagnosis was reported by 21 (0.5%) workers; and of these, 90.5% had a reactive IgG result. Seroprevalence was higher among those reporting contacts with confirmed cases, having been quarantined, using a previous molecular negative test or having had symptoms. Conclusions The seroprevalence among workers from the three public higher education institutions of Porto after the first wave of the SARS-CoV-2 contamination was similar to national estimates for the same age working population. However, the estimated true seroprevalence was approximately five times higher than the reported SARS-CoV-2 contamination based on a molecular Rabbit Polyclonal to PPP2R3C test. strong Paliperidone class=”kwd-title” Keywords: COVID-19, Epidemiology, Occupational Health, Public Health Surveillance Key messages What is already known about this subject? Seroprevalence studies are essential to know the real extension of SARS-CoV-2 contamination, populace immunity and workplace risk. Among the working population, studies are mostly concerned with healthcare workers. What are the new findings? The true prevalence of SARS-CoV-2-specific antibodies among workers of the higher education institutions of Porto, Portugal by the end of the first SARS-CoV-2 wave was 2.5% (95% CrI 0.1% to 5.3%), five occasions greater than the self-reported period prevalence of SARS-CoV-2 contamination as diagnosed by a molecular test (0.5%). How might this impact on policy or clinical practice in the foreseeable future? These results provide a baseline extension of the Paliperidone SARS-CoV-2 contamination in a working population that encompasses a wide range of socioeconomic positions and different levels of risk exposure. Introduction The SARS-CoV-2 contamination can cause very severe disease, particularly among individuals with underlying conditions. Commonly it progresses unnoticed with few or no symptoms1additional limited testing capacity has led to a variable undiagnosed rate. Seroprevalence studies are based on the identification of SARS-CoV-2-specific antibodies. In this case of an emergent agent, the entire populace is usually initially susceptible. Therefore, the presence of specific antibodies provides estimates of the cumulative incidence of Paliperidone contamination. In SARS-CoV-2 contamination, almost all of the infected individuals seroconvert Paliperidone within 2C3 weeks.2C4 Diseases with an impact around the working populace cause very high individual and societal costs. Activities where interpersonal contact is inevitable, structural or individual lack of compliance with preventive steps, sharing the same office or canteen space, and meeting in overcrowded rooms may increase the SARS-CoV-2 contamination in the workplace.5 Preventive measures include the use of face masks, hand sanitisers, increased distance between workers, scattered working hours or working from home. The latter has been deemed mandatory in Portugal from 18 March to 30 June 2020. The return to workplace activities provided an excellent opportunity to obtain data on serum status. Only a few studies have been conducted among higher education workers.6C8 Therefore, we aimed to assess the prevalence of SARS-CoV-2-specific IgM and IgG antibodies among workers of public higher education institutions of Porto, Portugal from May to July 2020. Methods All workers of the three public higher education institutions of Porto city were offered a serological point-of-care test for SARS-CoV-2-specific IgM and IgG antibodies from 21 May to 31 July 2020. Participation was voluntary, and scheduling was Paliperidone initiated by the workers. At the day of testing, workers were invited to answer to two questionnairesone to evaluate clinical aspects, conducted by the trained researcher who performed the test, and another self-administered to address sociodemographic characteristics. The clinical questionnaire included information on comorbidities, contacts with confirmed SARS-CoV-2 cases in the previous 2?weeks, symptoms since the beginning of 2020 (categorised into asymptomatic; moderately symptomatic (one or two of the following symptoms: cough, dyspnoea, odynophagia, headache, vomiting or nausea, diarrhoea, asthenia or fever); and symptomatic (at least three of the listed symptoms, or dysgeusia or anosmia)), and previous SARS-CoV-2 diagnostic tests. The self-administered questionnaire inquired about gender identity, nationality, educational level, occupation, currently working from home, self-perception of having been infected, travelling abroad since December 2019, contacts with confirmed SARS-CoV-2 cases and having been quarantined since January 2020. Participants provided written informed consent to all procedures. SARS-CoV-2-specific IgM and IgG antibodies determination and follow-up Two point-of-care tests were usedthe.