Why is a school-age boy unlikely to contract chicken pox again after having the disease in childhood?

The reason a school-age boy is unlikely to contract chicken pox again after having the disease in childhood is due to active immunity from antibody production. When a person contracts chicken pox (caused by the varicella-zoster virus), the immune system responds by producing antibodies specifically designed to target that virus. This immune response not only eliminates the virus during the initial infection but also leads to the formation of memory cells.

These memory cells enable the immune system to recognize and respond more rapidly and effectively if the person is exposed to the virus again in the future. As a result, the individual typically develops long-term immunity, making it very unlikely for them to experience chicken pox a second time.

While passive immunity may provide temporary protection through maternal antibodies, it does not apply in this case since the boy has already had the disease and built his own immune response. Genetic resistance and environmental factors may play roles in disease susceptibility but do not directly explain the robust immunity developed from previous infection.