[Objective]To evaluate the protective effectiveness of PCV7 vaccination in children aged 2-5 years. [Methods]PCV7 vaccination records for all children aged 2-5 years in Shaoxing City over the past 10 years were retrospectively collected from the medical information management system. Univariate and multivariate analyses were performed to assess the protective effect of PCV7. Causal forest and Cox Forest models were further introduced to analyze theheterogeneity in PCV7 protection. [Results]The 10-year follow-up data showed that the cumulative incidence in the vaccinated group was 1.30% （56/4321），significantly lower than the 5.07% （219/4321）in the control group，with a risk ratio of 0.256 （P<0.001） and a vaccine efficacy of 74.4%. Multivariate analysis and the causal forest model （ATE = -0.324）further confirmed the protective effect of the vaccine，which was more pronounced in younger children. Long-term follow-up indicated temporal fluctuations in protection，yet efficacy remained high throughout the 10-year period. [Conclusion]PCV7 vaccination demonstrates significant protective effectiveness in the majority of the population and plays a substantial role in reducing the risk of pneumonia incidence. Keywords：PCV7；Children aged 2-5 years；Protective effectiveness