Assessing the risk of vaccine-driven virulence evolution in SARS-CoV-2
Abstract
How might COVID-19 vaccines alter selection for increased SARS-CoV-2 virulence, or lethality? Framing current evidence surrounding SARS-CoV-2 biology and COVID-19 vaccines in the context of evolutionary theory indicates that prospects for virulence evolution remain uncertain. However, differential effects of vaccinal immunity on transmission and disease severity between respiratory compartments could select for increased virulence. To bound expectations for this outcome, we analyze an evo-epidemiological model. Synthesizing model predictions with vaccine efficacy data, we conclude that while vaccine driven virulence evolution remains a theoretical risk, it is unlikely to threaten prospects for herd immunity in immunized populations. Given that this event would nevertheless impact unvaccinated populations, virulence should be monitored to facilitate swift mitigation efforts.
Significance statement
Vaccines can provide personal and population level protection against infectious disease, but these benefits can exert strong selective pressures on pathogens. Virulence, or lethality, is one pathogen trait that can evolve in response to vaccination. We investigated whether COVID-19 vaccines could select for increased SARS-CoV-2 virulence by reviewing current evidence about vaccine efficacy and SARS-CoV-2 biology in the context of evolutionary theory, and subsequently analyzing a mathematical model. Our findings indicate that while vaccine-driven virulence evolution in SARS-CoV-2 is a theoretical risk, the consequences of this event would be limited for vaccinated populations. However, virulence evolution should be monitored, as the ramifications of a more virulent strain spreading into an under-vaccinated population would be more severe.
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