Number and recall of each type of letter. Recall interval is the gap between birthday and interview dates
| Age | Health message | Letters sent n | Completed interviews n (%) | Correctly identified topic % (95% CI) | Recall interval Mean days (range) |
|---|---|---|---|---|---|
| 12 | Smoking | 33 | 16 (48) | 88 (71–100) | 43 (39–47) |
| 12 | Immunisation | 31 | 17 (55) | 47 (23–71) | 42 (39–46) |
| 13 | Smoking | 30 | 18 (60) | 83 (66–100) | 42 (40–52) |
| 13 | Sun exposure | 32 | 20 (63) | 45 (23–67) | 42 (39–50) |
| 14 | Smoking | 33 | 21 (63) | 90 (78–100) | 43 (40–52) |
| 14 | Diet | 33 | 22 (67) | 59 (39–80) | 42 (38–47) |
CI = confidence intervals.