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

Area of Science:

• Infectious Diseases
• Vaccinology
• Epidemiology

Background:

• The 7-valent pneumococcal conjugate vaccine (PCV7) has reduced invasive pneumococcal disease (IPD) but faces challenges from serotype replacement.
• Understanding serotype dynamics is crucial for optimizing pneumococcal vaccination strategies, especially in Europe where PCV7 implementation is relatively recent.

Purpose of the Study:

• To evaluate the long-term impact of high PCV7 coverage on Streptococcus pneumoniae serotype distribution in Liguria, Italy.
• To assess the immunogenicity and effectiveness of PCV7 and introduce the 13-valent pneumococcal conjugate vaccine (PCV13).

Main Methods:

• A large-scale PCV7 vaccination program was implemented in Liguria in 2003, achieving over 90% coverage.
• Active and passive surveillance systems monitored invasive pneumococcal disease (IPD) and non-IPD.
• Immunogenicity of co-administered PCV7 and exavalent vaccine was evaluated using a 3-5-11 month schedule.

Main Results:

• Following PCV7 implementation, the proportion of PCV7 serotypes causing IPD and non-IPD significantly declined, accounting for approximately 10% by 2009-10.
• The introduction of PCV13 in 2010 offers expanded coverage, addressing approximately 90-100% of IPD and over 40-60% of non-IPD in children.

Conclusions:

• High PCV7 vaccination coverage effectively reduces targeted serotypes, demonstrating the potential for long-term success in Europe.
• PCV13 provides a significant advantage by covering a broader range of pneumococcal serotypes, addressing the limitations of PCV7 and reducing the burden of IPD and non-IPD.