This study investigates the correlates of protection against symptomatic SARS-CoV-2 infection in vaccinated children aged 5–12 years. The study found that children who received two doses of BNT162b2 vaccine mounted robust antibody, memory B cell (MBC), and T cell responses, with higher levels of these responses compared to adults 6 months after vaccination. A booster dose only improved antibody titers without affecting MBC and T cell responses. Among children with hybrid immunity (i.e., those infected after vaccination), nAbs and T cell responses were highest in those infected after two vaccine doses. Binding IgG titers, MBCs, and T cell responses were predictive of protection against symptomatic infection, with T cells being the most important predictor before hybrid immunity. After hybrid immunity, nAbs became the primary correlate of protection. The study suggests that booster vaccinations do not provide additional immunological protection to healthy children and that primary vaccination should be completed within a 3–4-week interval to minimize infection between doses. These findings inform pediatric vaccination policies and highlight the importance of considering both humoral and cellular immune responses in vaccine development and public health strategies.This study investigates the correlates of protection against symptomatic SARS-CoV-2 infection in vaccinated children aged 5–12 years. The study found that children who received two doses of BNT162b2 vaccine mounted robust antibody, memory B cell (MBC), and T cell responses, with higher levels of these responses compared to adults 6 months after vaccination. A booster dose only improved antibody titers without affecting MBC and T cell responses. Among children with hybrid immunity (i.e., those infected after vaccination), nAbs and T cell responses were highest in those infected after two vaccine doses. Binding IgG titers, MBCs, and T cell responses were predictive of protection against symptomatic infection, with T cells being the most important predictor before hybrid immunity. After hybrid immunity, nAbs became the primary correlate of protection. The study suggests that booster vaccinations do not provide additional immunological protection to healthy children and that primary vaccination should be completed within a 3–4-week interval to minimize infection between doses. These findings inform pediatric vaccination policies and highlight the importance of considering both humoral and cellular immune responses in vaccine development and public health strategies.