Main outcome: Incidence of SARS-CoV-2 infection
The diagnosis of SARS-CoV-2 infection was performed using RT-PCR on nasopharyngeal swab (Allplex 2019-nCoV assay, Seegene) (Online supplement 2). 24 An RT-PCR multiple variant assay was used for the detection of α and β/γ variants (ID™ SARS-CoV-2/UK/SA Variant Triplex (id Solutions) and for genome sequencing.