Pneumococcal Conjugate Vaccine and Clinically Suspected Invasive Pneumococcal Disease

Abstract

OBJECTIVE: Ten-valent pneumococcal conjugate vaccine (PCV10) was earlier shown to reduce clinically suspected, non–laboratory-confirmed invasive pneumococcal disease (IPD) in a cluster-randomized trial (the Finnish Invasive Pneumococcal disease trial). PCV10 was introduced into the Finnish national vaccination program in September 2010 using a 3-dose schedule. We evaluated the impact of PCV10 on clinically suspected IPD among vaccine-eligible children in a population-based nationwide study. METHODS: The target cohort eligible for vaccination program (children born June 2010–September 2013) was compared with 2 season- and age-matched (ages 3–42 months) reference cohorts before PCV10 introduction. The trial period (January 2009–August 2010) was excluded. Hospitals’ inpatient and outpatient discharge notifications with International Classification of Diseases, 10th Revision, diagnoses compatible with IPD (A40.3/B95.3/G00.1/M00.1) and unspecified sepsis (A40.9/A41.9/A49.9/G00/G00.9/I30.1/M00/M00.9/B95.5) were collected from the national Care Register. Laboratory-confirmed IPD cases were excluded. Rates of register-based non–laboratory-confirmed IPD (or unspecified sepsis) before and after PCV10 implementation were calculated. RESULTS: The rate of register-based non–laboratory-confirmed IPD episodes was 32 in 100 000 person-years in the vaccine-eligible target cohort and 94 in the combined reference cohorts. Relative rate reduction was 66% (95% confidence interval: 59–73) and absolute rate reduction 62 in 100 000 person-years. For the more sensitive case definition of register-based non–laboratory-confirmed IPD or unspecified sepsis, the relative rate reduction was 34% (95% confidence interval 29–39), but the absolute reduction was as high as 122 in 100 000 person-years. CONCLUSIONS: This is the first report demonstrating nationwide PCV impact on clinically suspected IPD during routine vaccination program. The large absolute rate reductions observed have major implications for cost-effectiveness of PCVs.