[The importance of immune system activation and vaccination in pediatrics].

Vaccination has transformed child health worldwide, preventing millions of deaths from infectious diseases. Early life immune responses differ from adults due to the relative immaturity of innate and adaptive immunity, making early-life vaccination critical for individual and population-level protection. Vaccines mimic natural infection to induce targeted, controlled, and safe immune activation, promoting both effector responses and long-term immune memory while avoiding the risks of disease. Trained immunity, a form of innate immune memory induced by live attenuated vaccines, further enhances non-specific and heterologous protection in early life. Evidence consistently shows that pediatric vaccination is safe, does not overload the immune system, and is essential for individual health, herd immunity, and the prevention of disease resurgence. This communication highlights the immune mechanisms underlying vaccine responses, the distinctive features of the pediatric immune system, the public health impact of vaccination programs, and provides recommendations for optimizing immunization strategies.