Vaccination coverages among adults with high-risk clinical conditions in Madrid, Spain

Abstract

Abstract Background Adults with high-risk clinical conditions (AHRCC) are a priority group for vaccination. However, data on vaccination coverage among AHRCC remain scarce in the European Union and other comparable settings, often limited to influenza and COVID-19 vaccines. Objectives To evaluate coverage and factors associated with uptake in influenza, COVID-19 and pneumococcal vaccines among adults with HRCC (HIV, hematopoietic stem cell transplantation, solid organ transplantation, malignant hematological disorders, asplenia, and haemodialysis). Methods Population-based retrospective study using linked hospital (CMBD) and vaccination registry data in Madrid. Adults (≥18 years) with any episode of hospitalization or emergency care (2022–2023) and AHRCC were included. Vaccination coverage was estimated for influenza and COVID-19 (2024–2025 campaign) and pneumococcus (lifetime). Factors associated with vaccination were analysed using population-averaged logistic GEE models adjusting for age, sex, income, country of birth, comorbidity and healthcare utilization. Results A total of 33,217 healthcare episodes (15,759 AHRCC) were analysed. Coverage was 40.6% for influenza, 28.9% for COVID-19 and 78.6% for pneumococcal vaccination. Individuals born outside Spain showed substantially lower uptake across all vaccines (≈35–45% lower after adjustment). Socioeconomic gradients were observed for influenza and COVID-19, with higher uptake in higher income groups, but not for pneumococcal vaccination. Older age was strongly associated with uptake, while comorbidity showed limited influence. Emergency care use was associated with lower vaccination uptake. Conclusions Vaccination coverage in AHRCC was suboptimal for influenza and particularly for COVID-19, despite high pneumococcal uptake. Differences were observed according to socioeconomic factors. To improve protection, targeted interventions are needed to raise awareness, address structural barriers and improve access. Key messages • Vaccination coverage among adults with high-risk clinical conditions remains suboptimal for influenza and COVID-19, with differences observed across socioeconomic and demographic groups. • Targeted strategies are needed to improve vaccination uptake by addressing access barriers and strengthening prevention efforts among vulnerable high-risk populations.