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 approximately 10% (IRR 0.90; 95% CI [0.84-0.97]) in patients aged >or=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.