Secular trends (1990-2013) in serotypes and associated non-susceptibility of S. pneumoniae isolates causing invasive disease in the pre-/post-era of pneumococcal conjugate vaccines in Spanish regions without universal paediatric pneumococcal vaccination

This study analyzed temporal trends of non-susceptibility/serotypes in invasive pneumococci from Spanish regions where pneumococcal conjugate vaccines (PCVs) were not included in paediatric immunization programmes. All invasive pneumococcal isolates voluntarily sent to the Spanish Reference Laboratory for Pneumococci (January 1990-December 2013) from hospitals located in target study regions were analyzed by age group. The PCV estimated coverage in children <24 months was correlated with 13-valent PCV (PCV13) serotypes trends. A total of 28,124 invasive isolates were analyzed: 3138 (11.2%) from children <24 months, 2161 (7.7%) from children 24-59 months, 781 (2.8%) from children 5-14 years, and 22,044 (78.4%) from adults. The estimated coverage increased from 17.6% (2002) to around 40% (2010-2013). The percentage of PCV13 serotypes among all isolates over time followed a cubic significant trend (R2 = 0.884), with an increasing trend up to 2001 followed by a decrease (more prominent from 2010 onwards). The estimated PCVs coverage was significantly correlated with the decrease in the percentage of PCV13 isolates in children <24 months (r2 = 0.824) and in adults (r2 = 0.786), mainly due to decreases in serotypes 1 and 7F in adults, and in serogroup 6 and serotypes 7F and 19A in children <24 months. None of the non-PCV13 serotypes stood out with substantial increases in the last period. This study showed that the different serotypes (and its associated non-susceptibility trends) were not equally affected by low PCVs disposition. Lack of impact in certain serotypes as serotype 1 (in children 24-59 months), 6C (in all age groups), and 19A (in adults) suggests the need for increasing vaccine coverage in the target vaccine population to increase direct and indirect protection.