List items currently missing from the questionnaire that are needed to achieve the stated survey objectives:

place of vaccination (health centre or hospital number); disease history, birth order, rural or urban (but the geo coordinates can help)

List questionnaire items currently unrelated to achieving the stated survey objectives:

Individual number being surveyed (copy from household member form)

Photo file name(s) of digital photo(s)

Recommend how to improve the alignment between questionnaire and the stated survey objectives.

Questionnaires are on multiple sheets and not very useful

Child can receive different vaccines from different practices (not common but can happen)

Test the questionnaire for easy completion

Use validated questionnaires which worked well previously

Reduce the number of unnecessary questions

Test how the electronic version of the questionnaire will look like

What steps would you take to ensure that interviewers ask the questions in the same standardized manner?

Training and using the check list; supervision and monitoring (for quality assurance and quality control)

What factors may contribute to ascertainment bias in this survey?

Bad recording and/or loss of vaccination cards or registers

Long questionnaire

Healthcare professional forgot to record the vaccine received