Vaccine hesitancy in conflict-affected Ukraine: An agent-based analysis of survey data.

BACKGROUND

In conflict-afflicted regions like Ukraine, disrupted health services, displacement, and logistical disturbances have compromised immunization and trust, underscoring the need to understand behavioral, access, and conflict dynamics for resilient strategies.

OBJECTIVE

To simulate the interaction between behavioral, structural, and social variables in predicting changes in vaccination beliefs and uptake in war-impacted Ukraine.

METHODS

We conducted a geographically diverse cross-sectional survey across 557 Ukrainian hromadas (local communities) during the ongoing war to assess vaccine confidence and behavioral determinants using an integrated psychological-computational framework. Empirical data were analyzed through k-means clustering and agent-based modeling (ABM) to simulate vaccination dynamics under conflict conditions. This survey-informed ABM examines how social contagion, healthcare access disruption, and conflict exposure may jointly shape vaccination behavior in a conflict-affected setting. To our knowledge, it represents one of the first behavioral simulation frameworks informed by survey data collected during the ongoing war in Ukraine.

RESULTS

Our agent-based modeling suggested that vaccination uptake in Ukraine is governed by a dynamic interplay between structural access and peer influence. Belief transitions reached 88%, whereas vaccination uptake increased 3%-15% due to access barriers. Conversely, peer dynamics increased vaccination coverage to 69%-89%, leading to a smoother coverage distribution. Sensitivity analyses indicated that peer conformity was the dominant driver, suggesting a collective mechanism linking social contagion and health behavior adoption.

CONCLUSION

Our findings suggest that structural access and peer influence jointly drive vaccine uptake during conflict, introducing a survey-based agent-based framework that links belief dynamics to behavior. These insights provide actionable pathways for equitable immunization policies in fragile and conflict-affected settings.