Immunization with the 7-valent conjugate pneumococcal vaccine: impact evaluation, continuing surveillance and future perspectives.

The 7-valent Pneumococcal Conjugate Vaccine (PCV) showed high efficacy against invasive pneumococcal diseases caused by vaccine serotypes in children less than 2 years-old. Its effectiveness was confirmed under routine use in the US, Canada and several European countries. Disease surveillance and several studies showed that population indirect protection outweighs direct protection of immunized subjects. A substantial impact was also confirmed on pneumonia and acute otitis media. A limited increase in IPD caused by non-vaccine serotypes was registered to date, but far below the magnitude of the beneficial reduction in IPD due to vaccine serotypes. This fact underpins the need for ongoing improved surveillance. New tests based on PCR for the identification and typing of pneumococci represent a very interesting alternative to traditional cultural tests that should be evaluated in the near future. The World Health Organization has recognized the priority to introduce PCV into the routine infant immunization schedule in all countries, due to the extremely high yearly mortality toll for pneumococcal diseases in the world (1.6 million deaths estimated). Conjugate vaccines with additional serotypes are in advanced stage of development or under evaluation. These new products need to be compared with the existing vaccine, following WHO recommendations regarding correlates of protection, in order to show their possibility to substitute the current vaccine obtaining the same impressive level of efficacy and effectiveness.