In-host modelling is a burgeoning field at the intersection of biology, mathematics, and computational science, dedicated to unravelling the intricate dynamics of disease and the immune system within individual hosts. The field has evolved significantly over time, driven by the need to understand how pathogens interact with the immune system and how interventions like treatments and vaccines can alter disease or infection outcomes. More work needs to be done to understand how genetic, environmental, and physiological factors affect how individuals respond to infections, vaccines, and treatments, influenced by variations in age, comorbidities, sex, ethnicity, immune-related genes, exposure histories, and overall health. Understanding these differences is crucial for advancing personalized and group-targeted medicines or vaccines, developing new drugs and vaccines, and optimizing public health programming for all populations. A workshop focus will be on key questions from industry and government through large and small group discussions. Industry and government reports will result.