Determinants of COVID-19 booster uptake in the Netherlands, autumn 2022: how well were those at risk for severe disease reached?

Background A booster with bivalent COVID-19 vaccine was offered in the Netherlands in autumn, 2022. We aimed to investigate vaccine uptake during the autumn 2022 booster round among the population subgroups at risk for severe COVID-19 that were specifically targeted by this campaign: the medical risk group aged 18-59 years and individuals ≥60 years. We calculated booster uptake in both populations and analyzed determinants of booster uptake among those who had received at least one prior COVID-19 vaccination. Methods Having had an autumn 2022 booster dose was defined as having received a COVID-19 vaccination between 19 September 2022 and 7 March 2023. The study population included individuals who received at least one previous COVID-19 vaccination. National registries of sociodemographic determinants and COVID-19 vaccination were linked by a unique person identifier. Voting proportions for political parties were included at neighborhood level. Determinants of COVID-19 vaccine autumn booster uptake were ranked by importance by random forest analyses. Results Booster uptake was 68% among those aged ≥60 and 30% among those aged 18-59 years with a medical risk factor for severe disease. For both target groups the most important determinant for booster uptake was age (15% in 18-29 years to 72% in 80+ years). Voting proportions for progressive liberal political parties ranked second in the random forest analysis in both groups, with an increasing proportion of votes associated with higher uptake. In the 60+ group, household type ranked third, with highest vaccine uptake among married couples without children (72%) and the lowest uptake among unmarried couples with children (47%). In the medical risk group, migration status ranked third. Migrants with two parents born abroad had the lowest uptake (18%), whereas migrants with both parents born in the Netherlands had the highest uptake (35%). Conclusion Among individuals who had received at least one prior COVID-19 vaccination, the autumn 2022 COVID-19 booster uptake was 68% in people ≥60 years and 30% in in the medical risk group aged 18-59 years. The most important determinant of booster uptake was age, followed by political preference and household type (60+ group) or migration status (medical risk group). Uptake varied considerably among subgroups in both target groups. Further research should be aimed at understanding the drivers and barriers of vaccine uptake among the subgroups with notably low uptake. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study 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 RIVM assessed the research proposal (EPI–613). 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 fulfil one or both of these conditions and therefore it is excluded 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 All data is available within CBS Microdata and can be made available under strict conditions.