Causes and consequences of undervaccination in adults

Despite progress in adult vaccination schedules, coverage rates remain suboptimal in Spain. This opinion paper, authored by a multidisciplinary group of experts, analyzes the causes and consequences of adult undervaccination, covering clinical, social, economic, and ethical aspects. Over 10 million individuals aged 65+ are targeted for vaccination, along with adults with chronic illnesses. However, coverage remains low, with significant disparities across vaccines, regions, and risk groups. The causes of the "vaccination gap" include lack of training among healthcare professionals, organizational barriers, misinformation, low-risk perception among the public, and weak institutional engagement. This situation leads to increased morbidity, mortality, and avoidable costs for the healthcare system. Universal adult vaccination could significantly reduce these burdens. The document outlines structured solutions: targeted professional training, multicomponent strategies, centralized vaccination registries, effective public awareness campaigns, improved access, and integration of vaccination across all healthcare levels. The key role of healthcare workers, patient organizations, and the media is emphasized in improving vaccination coverage.