Determinants for not keeping up to date with COVID-19 vaccination among medical risk groups

Abstract Vaccination is critical for preventing severe COVID-19 in medical risk groups (MRG). However, coverage has sharply declined among MRG in the Netherlands, from 19% in 2022 to 6% in 2023 (18-59 years) and from 61% to 53% (≥60 years). Understanding why individuals vaccinated in 2022 chose not to get vaccinated in 2023 (‘vaccination dropout’) is essential for designing targeted interventions to address declining coverage and protect at-risk groups. We explored determinants of vaccination dropout in 2023. We conducted a retrospective database study of MRG individuals aged ≥18 years in the Netherlands. Socio-demographic determinants for vaccination dropout were analysed using multivariable logistic regression. Among all MRG aged 18 years and older who were vaccinated in 2022 (n = 1,593,265), dropout in 2023 was 33%. Dropout was higher among MRG aged <60 years, particularly among younger individuals (aOR 18-24years 2.55; 95% CI: 2.34-2.78, reference: 55-59 years). Being in a household with children increased dropout, where non-married couples with children had an aOR of 1.63 (CI: 1.57-1.69, reference: married couples without children). For MRG aged ≥60 years, younger age (aOR 60-64years 2.26; CI: 2.21-2.31, reference: ≥80 years) and lower income (aOR lowest quartile 1.80; CI: 1.77-1.83, reference: highest income quartile) were strongly associated with dropout, respectively. In both age groups, lower medical risk, being born abroad, living in a non-urban area and lack of car-ownership increased dropout. Being employed and living <5km from vaccination sites were associated with lower dropout. COVID-19 vaccine coverage among MRG in the Netherlands declined in 2023 compared to 2022. We identified several determinants for dropout relevant for programme optimization. Targeted, tailored interventions to improve vaccine access and address these barriers are critical, consistent with WHO recommendations for equitable immunization strategies. Key messages • Socio-demographic factors influence COVID-19 vaccination dropout, emphasizing the need for targeted policy and programmatic interventions. • Dropout determinants align with those of never-vaccinated individuals, targeted & tailored interventions could address both groups, improving vaccine coverage and closing gaps per WHO recommendations.