Background: Efficacy of vaccines studied in clinical trial settings are likely to be different from their effectiveness in a real-world scenario. Indian Armed Forces launched its vaccine drive against COVID-19 on 16 Jan 2021. This study evaluated the effect of vaccination on mortality amongst hospitalized COVID patients. Methods: A cross sectional study was done on all admitted moderate to severe COVID-19 patients at a designated COVID hospital in New Delhi. The primary outcome assessed the association of being fully vaccinated with mortality. Unadjusted odds ratios (OR) (with 95% CI) was performed for each predictor. Logistic regression was used for multivariable analysis and adjusted odds ratios obtained. Results: The 1168 patients included in the study had a male preponderance with a mean age of 54.6 (+/- 17.51) years. A total of 266 (23%) patients were partially vaccinated with COVISHIELD(R) and 184 (16%) were fully vaccinated. Overall, 518 (44.3%) patients had comorbidities and 332 (28.4%) died. Among those fully vaccinated, there was 12.5% (23/184) mortality while it was 31.45 % (309/984) among the unvaccinated (OR 0.3, 95% CI 0.2 to 0.5, p<0.0001). In a logistic regression model, complete vaccination status and younger age were found to be associated with survival. Conclusions: Vaccination with two doses of COVISHIELD(R) was associated with lower odds of mortality among hospitalized patients with moderate to severe COVID.