Incidence of invasive pneumococcal disease among elderly people in Southern Catalonia, Spain, 2002–2009: An increase in serotypes not contained in the heptavalent conjugate vaccine

Abstract

Population-based surveillance study conducted among persons ≥ 65 years old in Southern Catalonia, Spain during 2002-2009. All cases with isolation of pneumococcus from normally sterile bodily fluids were included. Incidence rates of invasive pneumococcal disease (IPD) as well as rates of infections caused by serotypes included in the heptavalent pneumococcal conjugate vaccine (PCV7) and the 23-valent polysaccharide pneumococcal vaccine (PPV23) were compared for early (2002-2005) and contemporary (2006-2009) periods. Mean incidence rate (per 100,000 population-year) of IPD across study period was 48.0 [95% CI (confidence interval): 30.1-72.5]. Incidence rates for PCV7 serotypes slightly decreased by 21% between 2002-2005 and 2006-2009 (from 9.2 to 7.3; p = 0.511) whereas rates of IPD due to nonPCV7 serotypes largely increased by 172% (from 15.6 to 42.4; p < 0.001) during the same period. For PPV23 but nonPCV7 types, incidence rates increased by 146% (from 10.9 to 26.9; p < 0.001) whereas rates for nonPPV23 serotypes increased by 237% (from 4.6 to 15.5; p = 0.001). As an overall effect of these changes, the incidence of all IPD increased by a significant 69% (95% CI: 29%-110%). Specific incidence rates of serotypes 6A (from 1.7 to 4.1; p = 0.182), 7F (from 1.7 to 5.7; p = 0.052) and 19A (from 0.6 to 6.2; p = 0.004) substantially increased between both periods. According to these findings, Southern Catalonia region can be classified as a mesoendemic area of pneumococcal infections among elderly people, with a recent increase incidence of some nonPCV7 serotypes (especially 19A).