[Impact of 7-valent pneumococcal conjugate vaccination in a population with low to intermediate vaccination levels].

Objective: To analyze the changes occurring in declared cases (microbiological report) of invasive pneumococcal disease (IPD) in children <2 years old in Catalonia (Spain) after the 7-valent pneumococcal conjugate vaccine (PCV7) was licensed for use.
Material and Methods: Cases of IPD in children <2 years old were obtained from notifications to the Microbiological Reporting System of Catalonia (MRSC) in 1997-1999 and 2002-2004 by the hospitals (n=23) that have participated in the MRSC continuously and uninterruptedly since its inception in 1995.
Results: Overall reported rates were 49.2 cases per 100,000 persons-year in 1997-1999 and 40.4 per 100,000 persons-year in 2002-2004; the difference was not statistically significant. The rate of bacteremic pneumonia fell from 25.2 per 100,000 persons-year in 1997-1999 to 21.6 per 100,000 persons-year in 2002-2004, and meningitis from 6.0 to 4.3 per 100,000 persons-year; again, differences were not statistically significant (P>0.05).
Conclusions: After PCV7 was licensed for use, a noticeable, but non-significant, reduction in reported IPD rates in children <2 years old occurred in Catalonia. If the results had been statistically significant, the overall reduction would have been 17.90%, not far below the theoretically expected reduction (22%), based on the protective efficacy of PCV7 (89%), the percentage of invasive disease-causing serotypes included in the vaccine (70%), and the vaccination coverage achieved during the study period (35%).