“Effectiveness of COVID-19 Vaccines in preventing Infectiousness, Hospitalization and Mortality: A Historical Cohort Study Using Iranian Registration Data During Vaccination program”

Background There are some concerns about the effectiveness of the inactivated and vector-based vaccines against SARS-CoV-2 in the real-world settings with the emergence of new mutations, especially variants of concern. Data derived from administrative repositories during mass-vaccination campaigns or programs are of interest to study vaccine effectiveness (VE). Methods Using 4-repository administrative data linkage, we conducted a historical cohort study on a target population of 3,628,857 inhabitants aged at least 18 years residing in Southern Iran. Results We estimated 71.9% [95% CI: 70.7-73.1%], 81.5% [95% CI: 79.5-83.4%], 67.5% [95% CI: 59.5-75.6%], and 86.4% [95% CI: 84.1-88.8%] hospitalization reduction for those who received the full vaccination schedule of BIBP-CorV, ChAdOx1-S/nCoV-19, rAd26-rAd5, and BIV1-CovIran vaccines, respectively. A high reduction in mortality – at least 85% – was observed in all age subgroups of fully immunized population. Conclusion The pragmatic implementation of a vaccination plan including all available vaccine options in the Iranian population was associated with a significant reduction in documented COVID-19 infection, hospitalization, and death associated with COVID-19. Key points The mass vaccination program with implementing a group of vaccines, that even for some of them (rAd26-rAd5, and BIV1-CovIran vaccines) have been only regionally authorized for emergency use, has been associated with a dramatic reduction in documented COVID-19 infection, as well as in hospitalization and deaths related to the COVID-19 diagnosis. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was not financially supported. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Biomedical Research Ethics Committees of Shiraz University of Medical Sciences gave ethical approval for this work (code: IR.SUMS.REC.1400.486; link: ethics.research.ac.ir/PortalProposalList.php?code=&title=%C7%CB%D1%C8%CE%D4%26%231740%3B&name=%E3%DE%CF%E3%26%231740%3B&stat=&isAll=&GlobalBackPage=https%3A%2F%2Fethics.research.ac.ir%2FPortalCommittee.php%3Fpage%3D3%26perPage%3D100%26order%3D%26lastorder%3D%26code%3DIR.SUMS.MED.REC) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The data repositories generated during the current study are not publicly available; however, would be available from the corresponding author on reasonable request to the Shiraz University of Medical Sciences, Vice Chancellor of Research.