Covid lockdown and repaying the immunity debt in children

Non-pharmaceutical interventions (NPIs) implemented during the SARS-CoV-2 pandemic have been proven effective. While reducing SARS-CoV-2 transmission, NPIs also reduced children's exposure to other pathogens, leading to a decline in the incidence of many viral and bacterial infections. The reduction in contact with viruses and bacteria could result in insufficient immune stimulation of pathogens in the population, leading to an increase in susceptible populations and a decline in herd immunity, which form the immunity debt during the SARS-CoV-2 pandemic. Immunity debt can impact the pattern of seasonal pathogens, increase the incidence and severity of invasive infections, and potentially raise the risk of allergic diseases in children. Immunization, continuing to implement NPIs, pathogen monitoring, and health education are important measures to repay immunity debt. Besides, trained immunity, referring to the memory immunity produced by the innate immune system upon re-stimulation, can be employed as a non-specific measure to prevent the spread of pathogens. The protective effect of trained immunity can be used as a temporary preventive measure for emerging infectious diseases and create conditions for vaccine development.