Manuscript title: The incidence and in-hospital mortality of COVID-19 patients post-vaccination in eastern India Authors:Abhraneel Guha 1 ,Aritra Chakrabarti 2 ,Subhrojyoti Bhowmick 3 ,Saibal Das 4 ,Rahul Khandelwal 5 ,Aditya Kumar 5 ,Ajoy Krishna Sarkar 6 ,Anupam Das 7 ,Krishnangshu Ray 8 ,Sujit KarPurkayastha 9 1 Senior Registrar -Internal Medicine, Peerless Hospital and B.K.Roy research centre,2Junior Resident,Department of Internal Medicine,Peerless hospital and B.K.Roy research centre 3 Clinical Director-Academics Peerless Hospital and B.K.Roy research Centre,Kolkata, 4 Indepedent Clinical Pharmacology Consultant, 5 DNB Internal Medicine PGT,Peerless hospital and B.K.Roy research Centre, 6 Clinical Director of Critical Care Unit ,Peerless hospital and B.K.Roy research centre, 7 Department of Medical Administration Peerless hospital and B.K.Roy research centre, 8 Medical Director Peerless hospital and B.K.Roy research centre, 9 Senior Consultant –Department of Gastroenterology,Peerless hospital and B.K.Roy Research centre. Corresponding author:Dr.Subhrojyoti Bhowmick, Associate Professor-Department of Pharmacology,KPC Medical College,Kolkata; email: drsubhro@gmail.com Abstract Objectives: The comparable effectiveness of Covishield and Covaxin vaccines has not been studied. We compared the effectiveness of Covishield and Covaxin vaccines against moderate to severe COVID-19. Methods: In this retrospective observational study, we collected data of patients who were admitted with moderate to severe COVID-19. The vaccination status and comorbidities of the patients were documented. The incidence and in-hospital mortality of COVID-19 patients was assessed. Univariate analysis was performed to determine the risk factors of in-hospital mortality. Results: Of 294 patients, 5.1% (n=15) received Covaxin and 26.5% (n=78) received Covishield; 68.4% (n=201) patients were unvaccinated. Of patients who were vaccinated and contracted COVID-19, 24.8% (n=73) had taken the first dose and 6.8% (n=20) had taken the second dose of either vaccine. The in-hospital mortality rate was 13.6% (n=40). 24/40 (60%) people who had hospital mortality were unvaccinated.3/40(7.5%) had succumbed to death after receiving double dose of Covishield ,11/40 (27.5%) had succumbed to death after receiving single dose of Covishield, 2/40(5%) had succumbed to death after receiving single dose of Covaxin, none had reported infection after receiving second dose of Covaxin. No significant association was found with the type of vaccine and the in-hospital mortality (p=0.23). Significant associations with in-hospital mortality were found with the interval before COVID-19 disease and vaccination (OR, 3.02; p=0.01); and the presence of diabetes mellitus (OR, 2.13; p=0.02), cardiovascular diseases (OR, 2.11; p<0.001), and malignancy (OR: 2.33; p=0.0325). Conclusion: There was no significant difference in the effectiveness of Covaxin and Covishield in terms of the incidence of COVID-19 and in-hospital mortality. Diabetes mellitus, cardiovascular diseases, and malignancies had a significant association with in- hospital mortality in patients with moderate to severe COVID-19. Keywords: COVID-19, vaccine, effectiveness, protection, eastern India . CC-BY-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted July 22, 2021. ; https://doi.org/10.1101/2021.07.15.21260265 doi: medRxiv preprint NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.