Early effectiveness of heptavalent conjugate pneumococcal vaccination on invasive pneumococcal disease after the introduction in the Danish Childhood Immunization Programme

We evaluated the effectiveness of the heptavalent pneumococcal conjugate vaccine (PCV7) on invasive pneumococcal disease (IPD) 1 year after PCV7's introduction in the childhood immunization programme through a nationwide cohort study based on laboratory surveillance data. There was a decline in the overall incidence of IPD from 19.4 to 17.1 cases per 100,000 population (incidence rate ratios (IRR) 0.87; 95% confidence interval (CI) [0.81–0.96]), and of meningitis from 1.56 to 1.16 (IRR 0.74; 95% CI [0.57–0.97]) comparing pre-PCV7 (years 2000–2007) and PCV7 (year 2008) periods. In children <2 years, the incidence decreased from 54 to 23 cases per 100,000 (IRR 0.43; 95% CI [0.29–0.62]) and for vaccine-serotypes from 36.7 to 7.7 (IRR 0.20; 95% CI [0.09–0.38]). The incidence of IPD declined ∼10% (IRR 0.90; 95% CI [0.84–0.97]) in patients aged ≥2 years. The case fatality was 17% in both periods. The administration of PCV7 was followed by a marked decline in the incidence of IPD in both vaccinated and non-vaccinated individuals.