SARS-CoV-2 Vaccine Effectiveness and Breakthrough Infections Among Patients Receiving Maintenance Dialysis.

Rationale & objective: SARS-CoV-2 vaccine effectiveness and immunogenicity threshold associated with protection against COVID-19-related hospitalization or death in the dialysis population are unknown. Study

Design: Retrospective, observational study. Setting & participants: Adult patients without COVID-19 history receiving maintenance dialysis through a national dialysis provider and treated between February 1 and December 18, 2021, with follow-up through January 17, 2022. Predictor: SARS-CoV-2 vaccination status. Outcomes: All SARS-CoV-2 infections, composite of hospitalization or death following COVID-19. Analytical approach: Logistic regression was used to determine COVID-19 case rates and vaccine effectiveness.

Results: Of 16,213 patients receiving dialysis during the study period, 12,278 (76%) were fully vaccinated, 589 (4%) were partially vaccinated, and 3,346 (21%) were unvaccinated by the end of follow-up. Of 1,225 COVID-19 cases identified, 550 (45%) occurred in unvaccinated patients, and 891 (73%) occurred during the Delta variant-dominant period. Between the pre-Delta period and the Delta-dominant period, vaccine effectiveness rates against a severe COVID-19-related event (hospitalization or death) were 84% and 70%, respectively. In the subset of 3,202 vaccinated patients with at least one anti-spike immunoglobulin G (IgG) assessment, lower anti-spike IgG levels were associated with higher case rates per 10,000 days and higher adjusted hazard ratios for infection and COVID-19-related hospitalization or death. Limitations: Observational design, residual biases, and confounding may exist.

Conclusions: Among maintenance dialysis patients, SARS-CoV-2 vaccination was associated with a lower risk of COVID-19 diagnosis and associated hospitalization or death. Among vaccinated patients, a low anti-spike IgG level is associated with worse COVID-19-related outcomes.