Preexisting influenza specific immunity and vaccine effectiveness

Area of Science:

• Immunology
• Vaccinology
• Epidemiology

Background:

• Influenza vaccine effectiveness (VE) exhibits significant variability.
• Preexisting immunity, shaped by prior influenza exposure and vaccination, is increasingly recognized as a key factor influencing VE.
• Current methodologies for investigating individual immune histories are limited, hindering a deeper understanding of this phenomenon.

Purpose of the Study:

• To summarize existing evidence on how preexisting immunity affects influenza VE.
• To explore the influence of an individual's immune history, including initial exposure, first vaccination, and lifelong exposures, on vaccine response.
• To discuss the potential of pre-immunized animal models for studying the interplay between preexisting immunity and vaccine efficacy.

Main Methods:

• Review and synthesis of retrospective observational studies on influenza VE.
• Categorization of findings based on the timeline of individual immune history (first exposure, first vaccination, repetitive exposure).
• Discussion of the utility of pre-immunized animal models in immunological research.

Main Results:

• Retrospective studies confirm that preexisting influenza-specific immunity modulates VE.
• Individual immune history, from initial infection to repeated vaccinations, demonstrably influences vaccine response.
• Pre-immunized animal models offer a promising avenue for dissecting the immunological mechanisms underlying the interaction between prior immunity and vaccine antigens.

Conclusions:

• A comprehensive understanding of the mechanisms behind preexisting immunity is essential for enhancing influenza VE.
• Developing novel vaccine strategies necessitates addressing the impact of prior immune experiences.
• Pre-immunized animal models represent a valuable tool for validating immunological mechanisms and evaluating novel vaccine strategies compared to naive models.