Early COVID-19 vaccine effectiveness of XBB.1.5 vaccine against hospitalization and ICU admission, the Netherlands, 9 October - 5 December 2023

We present early vaccine effectiveness (VE) estimates of the 2023 seasonal COVID-19 vaccination campaign using XBB.1.5 vaccine against COVID-19 hospitalization and ICU admission in previously vaccinated adults ≥60 years old in the Netherlands. We compared vaccination status of 2050 hospitalizations including 92 ICU admissions with age group-, sex-, region- and date-specific population vaccination coverage between 9 October and 5 December 2023. VE against hospitalization was 70.7% (95% CI: 66.6; 74.3), VE against ICU admission was 73.3% (95% CI: 42.2; 87.6). ### Competing Interest Statement CHvW reports financial and non-financial research support from DaVolterrra and bioMerieux; financial research support from LimmaTech; consultancy fees from MSD and Sanofi-Pasteur (all payments to the University Medical Centre Utrecht). Other authors have nothing to report. ### 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 research proposal (reference EPI-520). They verified whether the work complies with the specific conditions as stated in the law for medical research involving human subjects (WMO), and were 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I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the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, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data are not publicly available due to privacy law.