Original antigenic sin: A potential double-edged effect for vaccine improvement.

Original antigenic sin (OAS) influences the immune response to subsequent infections with related variants following initial pathogen exposure. This phenomenon is characterized by cross-reactivity, which, although it may worsen infections, also provides a degree of protection against immune evasion caused by variations. This paradox complicates the development of creating universal vaccinations, as they frequently show diminished effectiveness against these emerging variants. This review aims to elucidate the diverse impacts of OAS on the immune response to various infections, emphasizing the complicated balance between beneficial and harmful outcomes. Moreover, we evaluate the influence of adjuvants and other variables on the extent of OAS, hence affecting the effectiveness of vaccines. Understanding the mechanisms of OAS that cause persistent infections and evasion of the immune system is crucial for the developing innovative vaccines. And it has significant potential for clinical applications.