A retrospective cohort study was conducted in 2631 Colombian children <2 yrs to evaluate pneumococcal vaccine effectiveness. Association between vaccination and disease was evaluated using Cox proportional hazards models. Vaccinated children had a significant reduction in hospitalization risk for all outcomes (HR 0,59 CI 95% 0,42 - 0,85) and for pneumonia the reduction was slightly higher (HR 0,53 CI 95% 0,32 - 0,89). Our results show an important risk reduction in clinical syndromes potentially associated to pneumococcus in vaccinated children confirming the benefits of using conjugate vaccines in a medium income developing country.