Nice work. Your CRF is very detailed. All the important variables and values are included and relatively grouped. The pattern, font size and format work very well.

I would like to point out few issues that could be adjusted,
– Demographic; Race/Ethnic could be added. Since study sites are in Bangkok and Chiangmai which are quite diversity community and that might affect the pre-vaccinated immunity status.
– The open-ended part could be reduced. The “if, please specify…” condition in many part of this CRF might not affect the outcome objectives.
– To minimize the redundancy, some questions in this CRF could be screened out. For example, the criteria in the eligibility part along with the assessment of eligibility part.
– Cumulative form is interesting. However, it could be arranged in multiple answers of associated disease that might be risky, for example, bleeding tendency, immunocompromised host, CKD. It might be more user friendly for data collectors if it’s put after page 3.