Figure 1.

Study populations and relationship to the whole dialysis population. The whole population at risk contains all of those receiving hemodialysis (in center) during the observation period. Weekly PCR screening was carried out in this population, with additional PCR testing as indicated by symptoms or contact with a case. The main study population (gray shading) contains all severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections defined by positive PCR (in any setting) during the observation period, and it is used to assess the risk of severe disease in those with infection. The supplementary study population (striped shading) contains a subset of the whole population at risk, for which full vaccination data were available, and it is used to assess the risk of developing infection. ^aWithin 14 days of positive PCR. ^bWithin 28 days of positive PCR.