1- Missing items:

no information planned in the questionnaire for:

-  rural and urban location of children
-  sex
- literacy of mother/caregiver

2- unrelated with the survey objectives:

- all the question on mobility around the routine immunization
- name of children
- name of mother/caregiver

3- how to improve the alignment between questionnaire and the stated survey objectives:

- deleting all the unrelated questions and inserting the missing one

4- Next steps to ensure that interviewers ask the questions in the same standardized manner:

- translating the question in the local languages
- and strongly training the interviewers according to standardized manner to ask

5- What factors may contribute to ascertainment bias in this survey?

- Determining age for certain children
- Poor conservation of health cards by mothers
- The investigators' level of understanding and how to ask questions