Vaccine-induced pathogen strain replacement: what are the mechanisms?

Area of Science:

• Evolutionary biology
• Immunology
• Epidemiology

Background:

• Host immune systems exert selective pressure on pathogens, driving pathogen evolution and the emergence of new antigenic signatures.
• Pathogen evolution involves complex interactions between within-host and population-level selection dynamics.
• Vaccination intensifies selection, potentially leading to vaccine-induced pathogen strain replacement.

Purpose of the Study:

• To review reports of subdominant pathogen variants emerging after vaccination campaigns.
• To extend existing models of pathogen strain replacement beyond differential vaccine effectiveness.
• To propose broader mechanisms driving pathogen evolution post-vaccination.

Main Methods:

• Review of existing literature on vaccine-induced pathogen strain replacement.
• Extension of theoretical models for pathogen strain replacement.
• Analogy drawn from ecological and evolutionary theories of competitive dynamics.

Main Results:

• Vaccination can promote the emergence of previously subdominant pathogen variants.
• Pathogen strain replacement can occur through mechanisms independent of differential vaccine effectiveness.
• Ecological trade-offs and life-history traits can influence pathogen competitive dominance and coexistence.

Conclusions:

• Existing models for vaccine-induced pathogen strain replacement are limited.
• New theoretical frameworks are needed to encompass broader evolutionary and ecological factors.
• Understanding these mechanisms is crucial for predicting and managing pathogen evolution in response to vaccination.