Mutation and SARS-CoV-2 strain competition under vaccination in a modified SIR model

Area of Science:

• Epidemiology
• Mathematical Biology
• Infectious Disease Dynamics

Background:

• COVID-19 pandemic highlighted the threat of emerging virus variants evading vaccine-induced immunity.
• Viral mutations increase the probability of concerning variants arising as infections accumulate.

Purpose of the Study:

• To develop a modified SIR model analyzing the competition between two infectious disease strains, one emerging via mutation.
• To investigate the impact of waning immunity and vaccination on strain competition and disease dynamics.

Main Methods:

• A modified susceptible, infected, and recovered (SIR) model incorporating waning immunity and vaccination was developed.
• The model characterizes parameter spaces, using vaccine efficiencies as control variables.
• Analysis included bifurcations between endemic and disease-free states to understand strain coexistence and extinction.

Main Results:

• Identified conditions for strain competition, including transient coexistence of two strains.
• Demonstrated that strain extinction can occur via competition or vaccination.
• Determined critical vaccine efficiencies required for disease eradication.

Conclusions:

• The mathematical model provides a quantitative tool for assessing vaccination policies against competing and emerging strains.
• Understanding disease dynamics is essential for managing epidemics with evolving pathogens.
• Vaccine efficiency is a key factor in controlling and potentially eradicating infectious diseases with variant emergence.