Impact of immunization-preventable infectious diseases on population health using disability-adjusted life years (DALYs) in Spain

Abstract Background The objective of this study is to estimate the burden of immunization-preventable infectious diseases in Spain using the Burden of Communicable Diseases in Europe (BCoDE) methodology and focusing on the national immunization program and potential new inclusions. Methods The BCoDE methodology relies on an incidence and pathogen-based approach to calculate disease burden via disability-adjusted life year (DALY) estimates. It considers short and long-term sequelae associated to an infection via outcome trees. The BCoDE toolkit was used to populate those trees with Spanish-specific incidence estimates, and de novo outcome trees were developed for four infections (herpes zoster, rotavirus, respiratory syncytial virus [RSV], and varicella) not covered by the toolkit. Age/sex specific incidences were estimated based on data from the Spanish Network of Epidemiological Surveillance; hospitalization and mortality rates were collected from the Minimum Basic Data Set. A literature review was performed to design the de novo models and obtain the rest of the parameters. The methodology, assumptions, data inputs and results were validated by a group of experts in epidemiology and disease modelling, immunization and public health policy. Results The total burden of disease amounted to 163.56 annual DALYs/100,000 population. Respiratory infections represented around 90% of the total burden. Influenza exhibited the highest burden, with 110.01 DALYs/100,000 population, followed by invasive pneumococcal disease and RSV, with 25.20 and 10.57 DALYs/100,000 population, respectively. Herpes zoster, invasive meningococcal disease, invasive Haemophilus influenza infection and hepatitis B virus infection fell behind in the ranking with less than 10 DALYs/100,000 population each, while the rest of infections had a limited burden (< 1 DALY/100,000 population). A higher burden of disease was observed in the elderly (≥ 60 years) and children < 5 years, with influenza being the main cause. In infants < 1 year, RSV represented the greatest burden. Conclusions Aligned with the BCoDE study, the results of this analysis show a persisting high burden of immunization-preventable respiratory infections in Spain and highlight for the first time a high number of DALYs due to RSV. These estimates provide a basis to guide prevention strategies and make public health decisions to prioritize interventions and allocate healthcare resources in Spain.