Effective health communication depends on the interaction of message source and content: two experiments on adherence to COVID-19 measures in Türkiye.

Objective: Following the COVID-19 outbreak, authorities recommended preventive measures to reduce infection rates. However, adherence to calls varied between individuals and across cultures. To determine the characteristics of effective health communication, we investigated three key features: message source, content, and audience.

Methods: Using a pre-test and two experiments, we tested how message content (emphasizing personal or social benefit), audience (individual differences), message source (scientists or state officials), and their interaction influence adherence to preventive measures. Using fliers advocating preventive measures, Experiment 1 investigated the effects of message content and examined the moderator role of individual differences. Experiment 2 presented the messages using news articles and manipulated sources.

Results: Study 1 found decreasing adherence over time, with no significant impact from message content or individual differences. Study 2 found messages emphasizing 'protect yourself' and 'protect your country' to increase intentions for adherence to preventive measures. It also revealed an interaction between message source and content whereby messages emphasizing personal benefit were more effective when they came from healthcare professionals than from state officials. However, message source and content did not affect vaccination intentions or donations for vaccine research.

Conclusion: Effective health communication requires simultaneous consideration of message source and content.