Strong social pressure to vaccinate should reduce infections. More people vaccinated, fewer susceptible hosts, lower transmission. But Roy et al. (arXiv: 2603.24403) show that dominant peer influence can increase long-term infection levels.
The model couples epidemic dynamics with opinion dynamics on a heterogeneous network. Individuals form vaccination opinions through two channels: local risk perception (seeing infections nearby drives pro-vaccination sentiment) and peer influence (conforming to the majority opinion in their social circle). Vaccination probability depends on the resulting opinion. The epidemic and the opinions co-evolve — infections shape opinions, opinions shape vaccination, vaccination shapes infections.
When local risk perception dominates, the system behaves intuitively: outbreaks trigger vaccination, which suppresses the epidemic, which reduces urgency, which reduces vaccination, which allows the next outbreak. This cycle is self-regulating. But when peer influence dominates, a different cycle emerges. Strong social pressure creates rapid vaccination consensus during an outbreak. The outbreak ends. Then the consensus — now driven by social conformity rather than perceived risk — sustains high vaccination even after the threat has passed. This suppresses the next outbreak so thoroughly that risk perception drops to zero. The conformity-driven opinion then has nothing to anchor it, and collective complacency sets in. The resulting vaccination collapse is deeper and more prolonged than what occurs under risk-driven dynamics.
The through-claim: social pressure amplifies the signal but destroys the feedback. Conformity creates vaccination surges that are too effective — they eliminate the visible threat that motivated vaccination in the first place. Risk-driven vaccination is self-correcting because the threat is its own reminder. Conformity-driven vaccination is self-undermining because its success erases its motivation. The stronger the social pressure, the deeper the complacency trough, and the larger the subsequent outbreak.
Roy, Shekhar, Ghosh, Kapitaniak & Hens, 2603.24403. Epidemiology / opinion dynamics / vaccination / network dynamics / social pressure.