Abstract
Although vaccines against seasonal influenza are designed to protect against currently circulating strains, they may also affect the emergence of antigenically divergent strains and thereby change the rate of antigenic evolution. Such evolutionary effects could change the benefits that vaccines confer to vaccinated individuals and the host population (i.e. private and social benefits). To investigate vaccinations potential evolutionary impacts, we simulated the dynamics of an influenza-like pathogen in an annually vaccinated host population. On average, vaccination decreased the cumulative amount of antigenic evolution of the viral population and the incidence of disease. Vaccination at a 5% random annual vaccination rate (48% cumulative vaccine coverage after 20 years) decreased cumulative evolution by 56% and incidence by 76%. To understand how the evolutionary effects of vaccination might affect its private and social benefits over multiple seasons, we fit linear panel models to simulated infection and vaccination histories. Including the evolutionary effects of vaccination lowered the private benefits by 14% but increased the social benefits by 30% (at a 5% annual vaccination rate) compared to when evolutionary effects were ignored. Thus, in the long term, vaccines' private benefits may be lower and social benefits may be greater than predicted by current measurements of vaccine impact, which do not capture long-term evolutionary effects. These results suggest that conventional vaccines against seasonal influenza could greatly reduce the burden of disease by slowing antigenic evolution like universal vaccines. Furthermore, vaccination's evolutionary effects compound a collective action problem, highlighting the importance on social policies concerning vaccination.
- Posted July 12, 2017.
