[Heptavalent-pneumococcal conjugate vaccine (Prevenar). Differences in effectiveness between populations]

Area of Science:

• Pediatrics
• Infectious Diseases
• Vaccinology

Background:

• Invasive pneumococcal disease (IPD) is a significant threat to children under five.
• The heptavalent-pneumococcal conjugate vaccine (PCV7) was introduced to prevent IPD.
• Pre-vaccine IPD serotype distribution varied globally, from 89% in the US to 43% in Asia.

Purpose of the Study:

• To review PCV7 effectiveness in preventing IPD in children under five.
• To analyze PCV7's impact on IPD epidemiology and serotype characteristics.
• To assess factors influencing PCV7's variable effectiveness.

Main Methods:

• Systematic review of publications on PCV7 effectiveness.
• Analysis of epidemiological data on IPD incidence and serotype distribution.
• Evaluation of vaccine impact based on laboratory-based surveillance.

Main Results:

• PCV7 introduction led to highly variable reductions in IPD incidence (91% in the US to 12% in Navarre, Spain).
• Global PCV7 effectiveness ranged from 31% to 89%, influenced by local pneumococcal serotype patterns.
• Evidence of serotype replacement by non-vaccine strains was observed, potentially reducing vaccine impact.

Conclusions:

• PCV7 effectiveness is significantly influenced by the prevalence of vaccine-preventable serotypes.
• Serotype replacement by non-vaccine strains can diminish the overall impact of PCV7.
• In regions with low vaccine serotype coverage (<70%), PCV7's effectiveness may be limited, suggesting targeted use for high-risk children.