Clinical Efficacy of the Fourth Dose of the BNT162b2 Vaccine in Maintenance Dialysis Patients.

Background and objectives Highly effective vaccines against severe acute respiratory syndrome virus 2 have been developed and administered worldwide. However, protection from coronavirus disease 2019 is not absolute and an optimal vaccination regimen needs to be established. This study assessed the clinical efficacy of the coronavirus disease 2019 vaccine among dialysis patients receiving 3 or 4 doses of vaccine. Design, setting, participants, and measurements This retrospective study was conducted using the electronic database of Clalit Health Maintenance Organization in Israel. Chronic dialysis patients treated with either hemodialysis or peritoneal dialysis during the coronavirus disease 2019 pandemic were included. We compared clinical outcomes of patients who had received three or four doses of the severe acute respiratory syndrome virus 2 vaccine. Results This study included 1,030 patients on chronic dialysis, with a mean age of 68 +/- 13 years. Among them, 502 patients had received 3 doses of the vaccine and 528 received 4 doses. Severe acute respiratory syndrome virus 2 infection rates, severe COVID-19 that resulted in hospitalizations, COVID-19-related mortality and all-cause mortality rates were lower among chronic dialysis patients who received a fourth dose of vaccine as compared to those who received only 3 doses (after controlling for age, sex and comorbidities). Despite lower mortality rates observed with the Omicron variant, the fourth dose was significantly associated with reduced COVID-19-related mortality (1.7% vs. 3.8%, p = 0.04). Odds ratio for COVID-19-related mortality was 0.44 with 95% CI 0.2-0.98. Conclusions As seen in the general population and with previous vaccine boosters, the fourth dose of the BNT162b2 vaccine reduced rates of severe COVID-19-related hospitalization and mortality among chronic dialysis patients. Further studies are needed to establish the optimal regimens of vaccination for patients on chronic dialysis.