The effect of pre-booked appointments on COVID-19 vaccine uptake during the 2023 autumn campaign in the Netherlands: a regression discontinuity analysis

Introduction There is evidence that pre-booked appointments (PBA) for vaccination can enhance uptake, but might also result in reactance. We assessed the effect of PBA (versus self-scheduling) on uptake of COVID-19 vaccination during the 2023 autumn campaign in the Netherlands.

Persons aged ≥60 years were personally invited by mail. Those born between 01-01-1934 and 01-05-1952 (i.e., age 71.7-90.0 on 31-12-2023) received a letter with a PBA, while the others received a letter inviting them to self-schedule an appointment. National registries of sociodemographic determinants and COVID-19 vaccination were linked by a unique personal identifier. A regression discontinuity design was applied to estimate the local average treatment effect at 71.7 and 90.0 years of age. Stratified analyses were done for sociodemographic subgroups.

The autumn 2023 vaccination coverage among persons aged ≥60 years with ≥1 prior registered COVID-19 vaccination (N = 4.0 million) was 55.0%. PBA resulted in a 3.3 (95% CI 2.6-4.1) and 4.5 (95% CI 2.8-6.3) percentage point higher uptake at 71.7 and 90.0 years, respectively. Subgroup analyses showed similar results. In one subgroup of migrants a negative effect of PBA was found, however, the confidence interval was wide.

This nationwide quasi-experimental study shows that PBA is predominantly effective in increasing uptake by reducing the intention-behaviour gap. However, differences between subgroups should be taken into account to increase equity of the vaccination programme. If PBA leads to a lower uptake in certain subgroups with already a relatively low uptake, disparities likely become larger. Competing Interest Statement The authors have declared no competing interest. Funding Statement This work was funded by the Dutch Ministry of Health Welfare and Sport. The funder had no role in in study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication. 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: This study received medical ethical clearance (EPI-649) by the Centre for Clinical Expertise (KEC) at the RIVM. The KEC is of the opinion that the research does not fulfil the conditions as stated in article one of the Dutch law for Medical Research Involving Human Subjects (WMO) nor in the EU Clinical Trial Directive (2001/20/EC). 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 Footnotes Figure 2 revised; Methods and Results clarified