OBJECTIVE: Protection against vaccine-preventable diseases is especially relevant in older adults due to age-related decline in immunity (immunosenescence). However, adult vaccination remains a challenge with overall low coverage rates, which has an impact on both the patients who have these diseases and the health care system in terms of resource use and costs derived. This study aimed to estimate the direct economic impact of herpes zoster, pneumococcal disease, influenza and pertussis in Spanish adults 45 years and older. METHODS: Data from 2015 were extracted from two Spanish public databases: the Minimum Basic Data Set for Hospitalisations and the Clinical Database of Primary Care. Codes from the International Classification of Diseases and the International Classification of Primary Care were used to identify and classify the diseases analysed. The variables extracted and calculated were hospitalisation (cases, percentage, length of stay, costs, mortality), primary care (cases, percentage, costs) and referrals (cases, percentage, costs). Results were presented for the age groups 45-64 years, 65-74 years, > 74 years and all ages. RESULTS: In adults 45 years and older, total costs amounted to €134.1 million in 2015 (i.e. 63.9% of the total direct costs for all age groups): 44.4% due to pneumococcal disease, 39.5% due to influenza, 16.0% due to herpes zoster and 0.1% due to pertussis. Hospitalisations represented 58.1% (€77.9 million) of the total costs, with 15,910 admissions, 144,752 days of hospitalisation and 1170 deaths. Primary care registered 566,556 visits with a cost of €35.0 million, and 269,186 referrals with a cost of €21.1 million. CONCLUSION: The direct economic burden of herpes zoster, pneumococcal disease, influenza and pertussis in adults 45 years and older was high in Spain, and may be underestimated as it only considered medical assistance and not other applicable direct or indirect costs. Increasing vaccination rates in adults may potentially reduce the economic burden derived from these diseases, although future cost-effectiveness analysis including other disease-related costs, vaccination costs and vaccination effectiveness would be needed.