# Social imitation dynamics of vaccination driven by vaccine effectiveness and beliefs

## TL;DR

The paper explores how beliefs about vaccines and social influences affect vaccination behavior and disease spread.

## Contribution

It introduces a model showing how coevolving vaccine beliefs can self-correct vaccine hesitancy.

## Key findings

- A small proportion of vaccine-averse beliefs can significantly worsen vaccination dilemmas.
- Coevolving vaccine beliefs can lead to self-correction and alignment with vaccination behaviors.
- Populations become more sensitive to changes in vaccine perceptions when beliefs coevolve.

## Abstract

Declines in vaccination coverage for vaccine-preventable diseases, such as measles and chickenpox, have enabled their surprising comebacks and pose significant public health challenges in the wake of growing vaccine hesitancy. Vaccine opt-outs and refusals are often fueled by beliefs concerning perceptions of vaccine effectiveness and exaggerated risks. Here, we quantify the impact of competing beliefs – vaccine-averse versus vaccine-neutral – on social imitation dynamics of vaccination, alongside the epidemiological dynamics of disease transmission. These beliefs may be pre-existing and fixed, or coevolving attitudes. This interplay among beliefs, behaviors, and disease dynamics demonstrates that individuals are not perfectly rational; rather, they base their vaccine uptake decisions on beliefs, personal experiences, and social influences. We find that the presence of a small proportion of fixed vaccine-averse beliefs can significantly exacerbate the vaccination dilemma, making the tipping point in the hysteresis loop more sensitive to changes in individuals’ perceived costs of vaccination and vaccine effectiveness. However, in scenarios where competing beliefs spread concurrently with vaccination behavior, their double-edged impact can lead to self-correction and alignment between vaccine beliefs and behaviors. The results show that coevolution of vaccine beliefs and behaviors makes populations more sensitive to abrupt changes in perceptions of vaccine cost and effectiveness compared to scenarios without beliefs. Our work provides valuable insights into harnessing the social contagion of even vaccine-neutral attitudes to overcome vaccine hesitancy.

Vaccination is one of the most cost-effective interventions for preventing and controlling infectious diseases, yet the world is experiencing declines in vaccination rates due to growing vaccine hesitancy. This hesitancy is often fueled by beliefs about vaccine effectiveness and perceived risks. Here, we study how these preexisting or coevolving beliefs, combined with social influences and personal experiences, shape vaccination behavior and affect disease spread. We find that even a small fraction of individuals with fixed vaccine-averse beliefs can create significant hurdles, making populations more sensitive to changes in perceived vaccine costs or effectiveness. Interestingly, this tipping-point fragility becomes less pronounced when vaccine beliefs coevolve and spread interpersonally. Our work underscores the importance of addressing both individual and social factors in promoting vaccination confidence and demand in the face of vaccine hesitancy.