The effect of social deprivation on the dynamic of SARS-CoV-2 infection in France : a population-based analysis

Publication notice : Vandentorren, Stéphanie, Sabira Smaïli, Edouard Chatignoux, Marine Maurel, Caroline Alleaume, Lola Neufcourt, Michelle Kelly-Irving, et Cyrille Delpierre. « The Effect of Social Deprivation on the Dynamic of SARS-CoV-2 Infection in France: A Population-Based Analysis ». The Lancet Public Health [Online] February 14, 2022.

Background : Data on health inequalities related to the dynamic of SARS-CoV-2 infection in France are scarce. The aim of this study was to analyse the association between an area-based deprivation indicator and SARS-CoV-2 incidence, positivity, and testing rates between May 2020 and April 2021.

Methods : We analysed data reported to the Système d’Information de Dépistage Populationnel surveillance system between May 14, 2020 and April 29, 2021, which records the results of all SARS-CoV-2 tests in France. Residential addresses of tested individuals were geocoded to retrieve the associated aggregated units for the statistical information (IRIS) scale, corresponding to an area comprising 2000 inhabitants relatively homogenous in terms of socioeconomic characteristics. A social deprivation score was assigned to each area using the European Deprivation Index (EDI). We fitted negative binomial generalised additive models to model the age-standardised and sex-standardised ratios for SARS-CoV-2 incidence, positivity rates, and testing rates, and to estimate incidence rate ratios (IRRs) and 95% CIs of their association with EDI quintiles, using the first quintile (least deprived) as the reference category, adjusted for week, population density, and region.

Findings : Analyses were based on 70 990 478 SARS-CoV-2 tests, of which 5 000 972 were positive. SARS-CoV-2 incidence was higher in the most deprived areas than the least deprived areas (IRR 1·148 [95% CI 1·138–1·158]) and positivity rates were also higher (IRR 1·283 [1·273–1·294]), whereas testing rates were lower in the most deprived areas than the least deprived areas (IRR 0·905 [0·904–0·907]). SARS-CoV-2 incidence and positivity rates remained higher in the most deprived areas than the least deprived areas during the second and third national lockdowns, and variation in testing rate was observed according to population density.

Interpretation : Our results highlight a positive social gradient between deprivation and the risk of testing positive for SARS-CoV-2, with the highest risk among individuals living in the most deprived areas and a negative social gradient for testing rate. These findings might reflect structural barriers to health-care access in France and lower capacity of deprived populations to benefit from protective measures.