ABSTRACT
ObjectivesThis cohort study including essential workers, assessed the{square}risk and incidence of SARS-CoV-2{square}infection during the second surge of COVID-19 according to baseline serostatus and occupational sector. MethodsEssential workers were selected from a seroprevalence survey cohort in Geneva, Switzerland and were linked to a state centralized registry compiling SARS-CoV-2 infections. Primary outcome was the number of virologically-confirmed infections from serological assessment (between May and September 2020) to January 25, 2021, according to baseline antibody status and stratified by three pre-defined occupational groups (occupations requiring sustained physical proximity, involving brief regular contact or others). Secondary outcomes included the incidence of infection. Results10457 essential workers were included (occupations requiring sustained physical proximity accounted for 3057 individuals, those involving regular brief contact, 3645, and 3755 workers were classified under "Other essential occupations"). After a follow-up period of over 27 weeks, 5 (0.6%) seropositive and 830 (8.5%) seronegative individuals had a positive SARS-CoV-2 test, with an incidence rate of 0.2 (95% CI 0.1 to 0.6) and 3.2 (95% CI 2.9 to 3.4) cases per person-week, respectively. Incidences were similar across occupational groups. Seropositive essential workers had a 93% reduction in the hazard (HR of 0.07, 95% CI 0.03 to 0.17) of having a positive test during follow-up with no significant between-occupational group difference. ConclusionsA ten-fold reduction in the hazard of being virologically tested positive was observed among anti-SARS-CoV-2 seropositive essential workers regardless of their sector of occupation, confirming the seroprotective effect of a previous SARS-CoV2 exposure at least six months after infection. Key messagesO_ST_ABSWhat is already known about this subject?C_ST_ABSRisk of SARS-CoV-2 reinfection is low in the general population and among healthcare workers. What are the new findings?A ten-fold reduction of risk of being virologically tested positive reinfection is observed among anti-SARS-CoV-2 seropositive essential workers of different activity sectors, regardless of their occupation-related risk of exposure. How might this impact on policy or clinical practice in the foreseeable future?Vaccination could be delayed in individuals with previous history of SARS-CoV-2 infection with serologic confirmation, regardless of their occupational exposure. These observations need to be confirmed for new SARS-CoV-2 variants.
ABSTRACT
PurposeThe Actionable Register of Geneva Out- and inpatients with SARS-CoV-2 (ARGOS) is an ongoing prospective cohort created by the Geneva Directorate of Health (GDH). It consists of an operational database compiling all SARS-CoV-2 test results conducted in the Geneva area since late February 2020. This article aims at presenting this comprehensive cohort, in light of some of the varying public health measures in Geneva, Switzerland, since March 2020. ParticipantsAs of June 1st, 2021, the database included 356868 patients, among which 65475 had at least one positive test result for SARS-CoV-2. Among all positive patients, 37.6% were contacted only once, 10.6 % had one follow-up call, 8.5% had two, and 27.7% had 3 or more follow-up calls. Participation rate among positive patients is 94%. Data collection is ongoing. Findings to dateARGOS data illustrates the magnitude of COVID-19 pandemic in Geneva, Switzerland, and details a variety of population factors and outcomes. The content of the cohort includes demographic data, comorbidities and risk factors for poor clinical outcome, self-reported COVID-19 symptoms, environmental and socio-economic factors, prospective and retrospective contact tracing data, travel quarantine data, and deaths. The registry has already been used in several publications focusing on symptoms and long COVID, infection fatality rate, and re-infection. Future plansThe data of this large real-world registry provides a valuable resource for various types of research, such as clinical research, epidemiological research or policy assessment as it illustrates the impact of public health policies and overall disease burden of COVID-19. STRENGTHS AND LIMITATIONS OF THIS STUDYO_LIARGOS main strength consists of its large number of cases, representative of all diagnosed cases on a regional level with the primary aim of assessing all cases. C_LIO_LIARGOS involves every individual who performed a SARS-CoV-2 test (PCR or antigenic) and is not limited to hospitalized patients, thus providing a valuable resource to assess the overall disease burden of COVID-19 in a geographically defined population. C_LIO_LITo mitigate confounding effects and improve data analysis and interpretation, we present the data according to four policy periods. C_LIO_LIThis cohort is multicentric as it includes all tests performed in Genevas hospitals (both public and private), private practices and medical centers. C_LIO_LIDue to operational needs, symptoms and comorbidities are self-reported, which may lead to measurement error or misclassification. C_LI
ABSTRACT
ImportanceSerological assays detecting specific IgG antibodies generated against the Spike protein following Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection are being widely deployed in research studies and clinical practice. However, the duration and the effectiveness of the protection conferred by the immune response against future infection remains to be assessed in a large population. ObjectiveTo estimate the incidence of newly acquired SARS-CoV-2 infections in seropositive individuals from a population-based sample as compared to seronegative controls. DesignRetrospective longitudinal propensity-score matched cohort study. SettingA seroprevalence survey including a population-based representative sample of the population from the canton of Geneva (Switzerland) was conducted between April and June 2020, immediately after the first pandemic wave. Each individual included in the seroprevalence survey was linked to a state centralized registry compiling virologically confirmed SARS-CoV-2 infections since the beginning of the pandemic. ParticipantsParticipants aged twelve years old and over, who developed anti-spike IgG antibodies were matched one-to-two to seronegative controls, using a propensity-score including age, gender, immunodeficiency, body mass index, smoking status and education level. ExposureSARS-CoV-2 seropositivity. Main outcomes and measuresOur primary outcome was virologically confirmed SARS-CoV-2 infections which occurred from serological status assessment in April-June 2020 to the end of the second pandemic wave (January 2021). Additionally, incidence of infections, rate of testing and proportion of positive tests were analysed. ResultsAmong 8344 serosurvey participants, 498 seropositive individuals were selected and matched with 996 seronegative controls. After a mean follow-up of 35.6 (Standard Deviation, SD: 3.2) weeks, 7 out of 498 (1.4%) seropositive subjects had a positive SARS-CoV-2 test, of which 5 (1.0%) were considered as reinfections. By contrast, infection rate was significantly higher in seronegative individuals (15.5%, 154/996) during a similar mean follow-up of 34.7 (SD 3.2) weeks, corresponding to a 94% (95%CI 86% to 98%, P<0.001) reduction in the hazard of having a positive SARS-CoV-2 test for seropositive subjects. Conclusions and relevanceSeroconversion after SARS-CoV-2 infection confers protection to successive viral contamination lasting at least 8 months. These findings could help global health authorities establishing priority for vaccine allocation. Key points QuestionDo SARS-CoV-2 antibodies confer protection against future infection? FindingsIn this retrospective matched cohort study nested in a representative sample of the general population of Geneva, Switzerland, we observed a 94% reduction in the hazard of being infected among participants with antibodies against SARS-CoV-2, when compared to seronegative controls, >8 months after initial serology assessment. MeaningSeroconversion to SARS-CoV-2 is associated with a large and sustained protection against reinfection.
