Socio-epidemiological model shows voluntary NPIs create shifting adherence games via prevalence feedback

The model integrates epidemiological dynamics with game-theoretic incentives, tracking how rising prevalence strengthens private-protection motives while source-control benefits invite free-riding and conformity amplifies the dominant behavior. At fixed prevalence the structure yields distinct games; as adherence lowers transmission the population traverses between these games, enabling bistability or oscillations not captured by static NPI analyses.

This framework directly addresses gaps in post-2020 observational data on mask and distancing uptake, where simple compliance models failed to predict persistent low adherence despite measurable risk reduction. By endogenizing the strategic environment the paper shows why identical population-level transmission effects can yield divergent long-term outcomes when protection is asymmetrically distributed between wearer and contacts.

Policy implications follow immediately: interventions that emphasize source control without addressing conformity thresholds risk locking populations into low-adherence equilibria, while balanced private-plus-source designs may stabilize intermediate adherence levels even after prevalence declines. Empirical tests require longitudinal behavioral-epidemiological panels that measure both individual protection motives and perceived social norms at multiple epidemic phases.