Number of COVID-19 hospitalisations averted by vaccination: Estimates for the Netherlands, January 6, 2021 through August 30, 2022

Background Vaccines against COVID-19 have proven effective in preventing COVID-19 hospitalisation. In this study, we aimed to quantify one aspect of the public health impact of COVID-19 vaccination by estimating the number of averted hospitalisations. We present results from the beginning of the vaccination campaign (period 1, January 6, 2021) and a period starting at August 2, 2021 (period 2) when all adults had the opportunity to complete their primary series, until August 30, 2022. Methods Using calendar-time specific vaccine effectiveness (VE) estimates and vaccine coverage (VC) by round (primary series, first booster and second booster) and the observed number of COVID-19 associated hospitalisations, we estimated the number of averted hospitalisations per age group for the two study periods. From January 25, 2022, when the indication of hospitalisation was registered, hospitalisations not causally related to COVID-19 were excluded. Results In period 1, there were an estimated 98,170 (95% confidence interval (CI) 96,123-99,928) averted hospitalisations, of which 90,753 (95% CI 88,790-92,531) in period 2, representing 57.0% and 67.9% of all hospital admissions. Estimated averted hospitalisations were lowest for 12-49-year-olds and highest for 70-79-year-olds. More admissions were averted in the Delta period (72.3%) than in the Omicron period (63.4%). Conclusion COVID-19 vaccination prevented a large number of hospitalisations. Although the estimated number of hospitalisations during the study period could not have realistically occurred due to capacity limits on health care, these findings underline the public health importance of the vaccination campaign to policy makers and the public. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was funded by the Dutch Ministry of Health, Welfare and Sports. ### 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: The Centre for Clinical Expertise at the RIVM assessed the above-mentioned research proposal. They verified whether the work complies with the specific conditions as stated in the law for medical research involving human subjects (WMO). They are of the opinion that the research does not fulfill one or both of these conditions and therefore conclude it is exempted for further approval by the ethical research committee. 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 primary data is not publicly available. Aggregated tables of these data are made available weekly at the website of the RIVM.