A study on the immune responses of vaccinated children aged 5–12 years found that two doses of BNT162b2 vaccine induced antibody, memory B cell (MBC), and T cell responses comparable to those in adults. Antibody and T cell responses were higher in children than in adults six months post-vaccination. A booster dose increased antibody titers but did not improve MBC or T cell responses. Children with hybrid immunity (infected after vaccination) had higher neutralizing antibody (nAb) and T cell responses. T cells were the most important predictor of protection against symptomatic infection before hybrid immunity, while nAbs were more relevant after hybrid immunity. Sustained MBC and T cell responses suggest long-term protection against symptomatic SARS-CoV-2 infection, even as nAbs wane. Booster vaccination did not provide additional protection to healthy children. The study, conducted in Singapore, involved 110 healthy children and 34 adults. Children received two doses of BNT162b2, while adults received two doses of 30 µg BNT162b2. The study found that hybrid immunity, where children were infected after vaccination, resulted in the highest immune responses. Children with hybrid immunity had higher nAb and T cell responses than those vaccinated only. T cell responses were more predictive of protection than nAbs. Booster vaccination did not improve immune responses in children with hybrid immunity. The study also identified immune correlates of protection against symptomatic SARS-CoV-2 infection. T cell responses were the most important predictor before hybrid immunity, while nAbs were more relevant after hybrid immunity. The findings suggest that T cell responses are crucial for protection against symptomatic infection, even when nAbs are insufficient. The study highlights the importance of T cell responses in protecting against SARS-CoV-2 infection, especially in children with hybrid immunity. The results indicate that booster vaccination may not be necessary for children with hybrid immunity, as their immune responses remain stable over time. The study provides insights into the immune correlates of protection against SARS-CoV-2 infection in children, which can inform vaccination policies for future birth cohorts.A study on the immune responses of vaccinated children aged 5–12 years found that two doses of BNT162b2 vaccine induced antibody, memory B cell (MBC), and T cell responses comparable to those in adults. Antibody and T cell responses were higher in children than in adults six months post-vaccination. A booster dose increased antibody titers but did not improve MBC or T cell responses. Children with hybrid immunity (infected after vaccination) had higher neutralizing antibody (nAb) and T cell responses. T cells were the most important predictor of protection against symptomatic infection before hybrid immunity, while nAbs were more relevant after hybrid immunity. Sustained MBC and T cell responses suggest long-term protection against symptomatic SARS-CoV-2 infection, even as nAbs wane. Booster vaccination did not provide additional protection to healthy children. The study, conducted in Singapore, involved 110 healthy children and 34 adults. Children received two doses of BNT162b2, while adults received two doses of 30 µg BNT162b2. The study found that hybrid immunity, where children were infected after vaccination, resulted in the highest immune responses. Children with hybrid immunity had higher nAb and T cell responses than those vaccinated only. T cell responses were more predictive of protection than nAbs. Booster vaccination did not improve immune responses in children with hybrid immunity. The study also identified immune correlates of protection against symptomatic SARS-CoV-2 infection. T cell responses were the most important predictor before hybrid immunity, while nAbs were more relevant after hybrid immunity. The findings suggest that T cell responses are crucial for protection against symptomatic infection, even when nAbs are insufficient. The study highlights the importance of T cell responses in protecting against SARS-CoV-2 infection, especially in children with hybrid immunity. The results indicate that booster vaccination may not be necessary for children with hybrid immunity, as their immune responses remain stable over time. The study provides insights into the immune correlates of protection against SARS-CoV-2 infection in children, which can inform vaccination policies for future birth cohorts.