On conducting diary-based social contact surveys to inform transmission models of close-contact infections: a systematic review and expert-informed questionnaire

An expert-informed questionnaire of 22 core items was developed from 36 retrievable general-population contact survey questionnaires, based on 26 experts, to harmonize diary-based studies.

• Why it matters: Diary-based social contact surveys are used to parameterise transmission models, but differences in design, contact definitions, and questionnaire content limit comparability, especially during COVID-19.
• What they did: A systematic review of 129 diary-based social contact studies across 62 countries (31 January 2018–25 September 2025) extracted methods and items, then 26 experts rated 54 items to select 22 core ones.
• The result: Updated recommendations on sampling, survey methods, contact definitions, behavioural change, essential contact information, and data governance aim to improve comparability and preparedness for future public health emergencies.

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