Are age-based strategies effective in increasing influenza vaccination coverage? The Spanish experience

We investigated the effectiveness of applying age-based strategies to improve influenza vaccination coverage in Spain. We described and compared influenza vaccination coverage from 2003 to 2010 between those Spanish autonomous regions (AR) that lowered the age limit to 60 y and those regions that maintained the limit at 65 y. We used data collected from two surveys covering a representative sample of the Spanish population aged >= 16 y [Spanish National Health Survey (SNHS) 2003/2004 and the European Health Survey for Spain (EHSS) 2009/2010]. The study population (persons aged >= 60 y) comprised 7,496 persons in the SNHS and 7,686 in the EHSS. In 2010, those AR which had reduced the age limit had higher coverage for all age groups analyzed-regardless of the presence of associated chronic conditions-than AR which continued vaccination for those >= 65 y. The greatest differences appeared in individuals aged 60 to 64 y (36.9% vs. 24.4% for individuals without chronic conditions, 59.1% vs. 52.9% for those with chronic conditions, and 43.3% vs. 32.3% for the entire age group). Multivariate analysis showed that those AR which lowered the age limit increased total coverage for all age groups, specifically among individuals with chronic conditions aged 60 to 64 y (IRR 1.18; 95% CI, 1.01-1.54) and >= 65 y (IRR 1.07; 95% CI, 1.00-1.14). No significant changes were observed over time for the AR that continued vaccinating people aged >= 65 y. Our results suggest that age-based strategies are effective for improving influenza vaccination coverage in Spain.