A pneumococcal conjugate vaccination programme reduced clinically suspected invasive disease in unvaccinated children

Area of Science:

• Pediatric Infectious Diseases
• Vaccinology
• Public Health Epidemiology

Background:

• The 10-valent pneumococcal conjugate vaccine (PCV10) was integrated into Finland's national child immunization schedule for births after June 2010.
• Evaluating indirect effects is crucial for understanding vaccine program impact.

Purpose of the Study:

• To assess the impact of the pneumococcal conjugate vaccine program on invasive pneumococcal disease (IPD) rates in unvaccinated children.
• To quantify the herd protection effect of the vaccination program.

Main Methods:

• An ecological, before-and-after study design was employed.
• Unvaccinated children born between January 2008-May 2010 (target cohort) were compared to age- and season-matched children born between January 2003-2005 (reference cohort).
• National hospital discharge data for IPD and unspecified sepsis were analyzed for the periods 2011-2014 and 2006-2009, respectively.

Main Results:

• Clinically suspected IPD incidence in unvaccinated children decreased by 68% (47 to 15 per 100,000 person-years).
• Including unspecified sepsis, the decrease was 39% (171 to 104 per 100,000 person-years).
• Laboratory-confirmed IPD incidence fell by 44% (15 to 8 per 100,000 person-years).

Conclusions:

• The pneumococcal vaccination program demonstrated significant herd protection against clinically suspected invasive pneumococcal disease.
• The observed reduction in suspected IPD was substantially greater than that for laboratory-confirmed cases, indicating a broad impact.