Correlation Between the SARS-CoV-2 Seroprevalence and the Theoretical Occupational Risk (TOR) and COVID-19 Morbidity Score (MBS) Among Local Public Workers in the Centre-Val de Loire Region – CovidOr Study

OBJECTIVE: To examine whether SARS-CoV-2 seroprevalence among local public workers in Centre–Val de Loire (France) was associated with a theoretical occupational risk (TOR) score and with a COVID-19 morbidity score (MBS). DESIGN, SETTING, AND PARTICIPANTS: CovidOr was a multicentre cross-sectional study conducted before widespread vaccination (August–December 2020) across Orléans Métropole, the Centre–Val de Loire Region, and the Communes of Terres du Val de Loire (CCTVL). A total of 3,602 municipal and regional employees (18-84 years) underwent rapid serological testing (COVID PRESTO®). EXPOSURE AND MEASURES: TOR summarised three job-related dimensions (daily exposure to disease/infection, daily public contact, and physical proximity; 0-3 points, grouped as low, moderate, high risk). MBS quantified higher-risk comorbidities for severe COVID-19 (0-5 points). A multivariable logistic regression modelled seropositivity (dependent variable) with age, sex, TOR, known COVID-19 contact, symptoms, centre, and MBS as covariates. Bonferroni correction set α=0.625%. RESULTS: Seropositivity was detected in 182/3,570 analysable participants (overall seroprevalence 5.1%). Mean age was 46.4 years; 66.6% were women. Neither age (OR 1.008; 95% CI 0.988-1.029; p=0.415) nor sex (OR 1.153; 0.731-1.819; p=0.541) was associated with seropositivity. Seroprevalence by TOR category was 0.08% (low), 2.28% (moderate), and 2.76% (high). Although TOR showed an unadjusted association (OR 1.70; 1.146-2.549; p=0.009), it was not significant after multiplicity correction (α=0.625%). Seropositive participants had a lower MBS (OR 0.752; 0.582-0.971; p=0.029), but this also lost significance after correction. Asymptomatic infections represented 31.9% of seropositive cases. Results were robust to adjustment for centre. CONCLUSIONS: In this large pre-vaccination cohort of local public workers, neither occupational risk as captured by TOR nor comorbidity burden (MBS) was independently associated with SARS-CoV-2 seropositivity after correction for multiple testing. These findings suggest that, in this setting, workplace contact intensity and aggregated comorbidity risk did not drive infection risk, underscoring the potential predominance of non-occupational exposures and the importance of universal prevention measures.