| Value | Category | Cases | |
|---|---|---|---|
| 1 | Clinic card/vaccination booklet | 3938 |
68.5%
|
| 2 | Respondent recall | 1659 |
28.9%
|
| 3 | Other written source | 16 |
0.3%
|
| 4 | Date of birth unknown | 3 |
0.1%
|
| Sysmiss | 130 |
2.3%
|