This study examines the impact of California's pediatric COVID-19 vaccination program on the incidence and hospitalization rates of SARS-CoV-2 infections among children. The study used a case series approach to analyze data from 3,913,063 pediatric cases and 12,740 hospitalizations between April 1, 2020, and February 27, 2023. The evaluation periods for post-vaccine effects were 141 days for adolescents aged 12 to 15 years, 199 days for children aged 5 to 11 years, and 225 days for children aged 6 to 59 months. During these periods, statewide vaccine coverage reached 53.5% for adolescents, 34.8% for children aged 5 to 11 years, and 7.9% for those aged 6 to 59 months. The results showed that the pediatric vaccination program was associated with significant reductions in COVID-19 incidence and hospitalizations. Specifically, the program averted 146,210 cases (37.1%) among adolescents aged 12 to 15 years, 230,134 cases (23.7%) among children aged 5 to 11 years, and 168 hospitalizations (24.4%) among children aged 6 to 59 months. Overall, the vaccination program averted 376,085 cases and 273 hospitalizations among children aged 6 months to 15 years over approximately 4 to 7 months following vaccine availability. The study also found that county-level vaccination coverage was associated with averted cases for all age groups, with each 10 additional vaccinations per 1000 children corresponding to a reduction of 0.9 to 3.5 cases per 1000 children. The findings suggest that the pediatric COVID-19 immunization program in California significantly reduced the incidence and hospitalization rates of SARS-CoV-2 infections among children.This study examines the impact of California's pediatric COVID-19 vaccination program on the incidence and hospitalization rates of SARS-CoV-2 infections among children. The study used a case series approach to analyze data from 3,913,063 pediatric cases and 12,740 hospitalizations between April 1, 2020, and February 27, 2023. The evaluation periods for post-vaccine effects were 141 days for adolescents aged 12 to 15 years, 199 days for children aged 5 to 11 years, and 225 days for children aged 6 to 59 months. During these periods, statewide vaccine coverage reached 53.5% for adolescents, 34.8% for children aged 5 to 11 years, and 7.9% for those aged 6 to 59 months. The results showed that the pediatric vaccination program was associated with significant reductions in COVID-19 incidence and hospitalizations. Specifically, the program averted 146,210 cases (37.1%) among adolescents aged 12 to 15 years, 230,134 cases (23.7%) among children aged 5 to 11 years, and 168 hospitalizations (24.4%) among children aged 6 to 59 months. Overall, the vaccination program averted 376,085 cases and 273 hospitalizations among children aged 6 months to 15 years over approximately 4 to 7 months following vaccine availability. The study also found that county-level vaccination coverage was associated with averted cases for all age groups, with each 10 additional vaccinations per 1000 children corresponding to a reduction of 0.9 to 3.5 cases per 1000 children. The findings suggest that the pediatric COVID-19 immunization program in California significantly reduced the incidence and hospitalization rates of SARS-CoV-2 infections among children.