Trained immunity: Immunological footprints and side-tracks

Vaccinations have significantly reduced mortality from infectious diseases by preparing the immune system for pathogens without causing illness. In addition to specific protection, some vaccines can also have non-specific effects (NSE), offering broader protection against various infections. This is explained by ‘trained immunity,’ where the innate immune system responds more quickly and strongly after prior stimulation. This concept could make vaccines more effective.This PhD research focused on NSEs and trained immunity, particularly in older individuals, through studies on the BCG vaccine and COVID-19 vaccines. One key finding was that administering flu and COVID-19 vaccines simultaneously might provide less protection than spacing them apart. Additionally, different types of COVID-19 vaccines appear to vary in their ability to induce non-specific effects. Finally, infectious diseases themselves can also trigger trained immunity, which may negatively impact how long patients continue to experience symptoms.