The impact of risk compensation adaptive behavior on the final epidemic size.

Public health interventions reduce infection risk, while imposing significant costs on both individuals and the society. Interventions can also lead to behavioral changes, as individuals weigh the cost and benefits of avoiding infection. Aggregate epidemiological models typically focus on the population-level consequences of interventions, often not incorporating the mechanisms driving behavioral adaptations associated with interventions compliance. In this study, we use a behavior-epidemic model to analyze the consequences of detrimental behavioral responses driven by risk compensation. We analyze scenarios with varying levels of vaccine-acquired immunity and study the trade-off between risk compensation behaviors and reduced susceptibility. Our results reveal a trade-off between imperfect vaccine-acquired immunity and the potential risk compensation behavior of vaccinated individuals. We find that the impact of vaccination is ultimately influenced by the risk compensation behaviors of vaccinated individuals, which can either increase or decrease the size of the epidemic depending on the vaccine effectiveness. Moreover, we show that the behavioral response of the susceptible population modulates the impact of compensation behaviors by vaccinated individuals. Our results highlight that the distribution of highly protective vaccines can mitigate the observed effect. Additionally, they emphasize the importance of concurrently implementing non-pharmaceutical interventions in scenarios wherein vaccines have low efficacy. We extend our model by incorporating a model of disease surveillance, which drives a realistic operational course of action based on testing, analysis and response. Our results highlight the importance of robust surveillance systems in providing early warnings of disease outbreaks, which trigger early behavioral responses and timely interventions.