Latar Belakang: Pneumonia (pneumonitis) merupakan penyakit infeksi yang banyak menyerang anak balita. Salat satu pencegahan dan pengendalian kasus pneumonia dilakukan melalui program pemberian imunisasi Pneumococcal Conjugate Vaccine (PCV) dengan sasaran balita. Pencapaian imunisasi pada saat itu masih di 71% atau berada di bawah target sebesar 100%. Tujuan : Tujuan Penelitian ini adalah Analisis Efektifitas Imunisasi PCV (Pneumococcal Conjugate Vaccine) dalam menurunkan angka kejadian kasus pneumonia pada Balita Di UPTD Puskesmas Rendang. Metode: Jenis analitik observasional Case-Control Study dengan pendekatan retrospektif. Penelitian ini dilakukan di UPTD Puskesmas Rendang pada bulan Maret – April 2025. Sampel yang digunakan berjumlah 85 balita dengan tehnik Proportionate stratified random sampling. Pengukuran variabel dilakukan menggunakan lembar extraksi data sekunder. Analisi dilakukan menggunakan uji Chi Square dan perhitungan Odds Ratio (OR). Hasil: Hasil penelitian menggunakan uji Chi Square terdapat hubungan yang signifikan antara imunisasi PCV dengan kejadian pneumonia (p-value< 0,001; ChiSquare=42,475). Nilai OR utama sebesar 0,028, menunjukkan bahwa anak yang diimunisasi memiliki risiko 96,8% lebih rendah untuk menderita pneumonia. Interval kepercayaan 95% (CI: 0,008-0,096) tidak melewati angka 1, menunjukkan imunisasi PCV merupakan faktor protektif yang signifikan. Kesimpulan: Imunisasi PCV terbukti efektif dalam menurunkan risiko kejadian pneumonia pada balita. Diperlukan peningkatan cakupan imunisasi melalui edukasi dan promosi kesehatan kepada masyarakat. Kata Kunci : Balita, Pneumonia,Imunisasi,Pneumococcal Vaccine (PCV)

Background. Pneumonia is a common infectious disease affecting children under five years old. One prevention and control measure is the Pneumococcal Conjugate Vaccine (PCV) immunization program targeting this age group. At the time of the study, PCV coverage was 71%, falling short of the 100% target. This study aimed to analyze the effectiveness of PCV immunization in reducing the occurrence of pneumonia cases among children under five years old at the Public Health Centre Rendang. Method. This analytical observational study employed a case-control design with a retrospective approach. The research was conducted at the Public Health Centre Rendang from March to April 2025. In this study, 85 under-five children were recruited using a proportionate stratified random sampling technique. Variables were measured through a secondary data extraction form. Data were analyzed using the Chi-Square test and Odds Ratio (OR) calculation. Results. Findings indicated that the Chi-Square test revealed a significant correlation between PCV immunization and pneumonia occurrence (p < 0.001; ChiSquare = 42.475). The OR was 0.028, indicating that immunized children had a 96.8% lower risk of developing pneumonia. The 95% confidence interval (CI: 0.008–0.096) did not cross 1, confirming PCV immunization as a significant protective factor. Conclusion. PCV immunization effectively reduces the risk of pneumonia among children under five. The coverage should be increased through community education and health promotion. Keywords: Under-Five Children, Pneumonia, Immunization, Pneumococcal Vaccine (PCV)