Epidemiological changes after PCV7 implementation in Italy: perspective for new vaccines.

The emergence of serotypes not included in 7-valent pneumococcal conjugate vaccine (PCV7), so-called "replacement", could erode the great advantage offered by vaccination. The effect of the replacement phenomena is very variable in different Countries and depends on one or more of several factors i.e. serotype before PCV7 implementation, PCV7 coverage, period from PCV implementation, vaccination schedule, antibiotic use, etc. The long-term epidemiological picture in Europe regarding serotype change is limited because of the relatively recent introduction of PCV7 - the majority of European Countries have only experienced PCV implementation since 2006 - and the difficulty in reaching very high vaccination coverage. In May 2003, a large-scale program of vaccination against Streptococcus pneumoniae with PCV7 was started in Liguria achieving coverage higher than 90%. The results of this program anticipate the results likely to be achieved when high coverage has been reached in Europe for a period of several years. The project included the immunogenicity evaluation of the co-administration of PCV7 and exavalent vaccine using the 3-5-11 month schedule, effectiveness evaluation and the active and passive surveillance system of invasive pneumococcal disease (IPD) and non-IPD. Since the beginning of PCV7 implementation, the proportion of PCV7 serotype has declined and in 2009-10 it accounted for about 10% of all Streptocuccus pn responsible for IPD and non-IPD. The new 13-valent pneumococcal conjugate vaccine, available since July 2010, will offer a significant added benefit covering about 90%, 100% of IPD and more than 40% and 60% of non-IPD detected in pre-school and school children, respectively, after PCV7 introduction.