question: Background: mRNA-based SARS-CoV-2 vaccines have been shown to be highly effective among dialysis patients. Because individual vaccines may be differentially available or acceptable to patients, it is important to understand comparative effectiveness of other vaccines, such those based on adeno-virus technologies. Methods: This retrospective study compared the clinical effectiveness of Ad26.COV2.S (Janssen/Johnson and Johnson) to BNT162b2 among dialysis patients. Patients initiating BNT162b2 (Pfizer/BioNTech) were matched 1:1 to Ad26.COV2.S recipients based on age, race, US state of residence, calendar week of first vaccine receipt, and history of COVID-19. The primary outcome was the comparative rate of COVID-19 considered over 3 follow-up intervals: weeks 1-3, 4-6, and [≥] 7 post-vaccination. In a subset of consented Ad26.COV2.S patients, blood samples were collected [≥]28 days after vaccination and anti-SARS-Cov-2 immunoglobulin G antibodies were measured. Results: There were 2659 matched pairs of patients who received a first dose of each vaccine. During weeks 1-3, incidence rates were 1.13 vs 1.39 per 1000 patient-weeks (pt-wks) for BNT162b2 and Ad26.COV2.S recipients, respectively (incident rate difference [IRD]: 0.25; 95% CI: 0.90, 1.36). During weeks 4-6, incidence rates were 0.78 vs 0.39 per 1000 pt-wks for BNT162b2 and Ad26.COV2.S recipients, respectively (IRD: -0.39; 95% CI: -1.16, 0.38). After week 7, incidence rates were 1.29 vs 1.39 per 1000 pt-wks for BNT162b2 and Ad26.COV2.S recipients, respectively (IRD: 0.10; 95% CI: -0.35, 0.55). Results were similar when considering only patients without a history of COVID-19 and among matched pairs in which BNT162b2 recipients completed the 2-dose regimen. SARS-CoV-2 antibodies were detected in 59.4% (95% CI: 53.0%-65.5%) of Ad26.COV2.S patients. Conclusion: In a large real-world cohort of dialysis patients, no difference was detected in the clinical effectiveness of BNT162b2 and Ad26.COV2.S, despite an inconsistent antibody response to the latter. These data support the use of either agent in ongoing vaccination efforts in this population.