Table 4. Indirect vaccine effectiveness against cholera using ring vaccination strategy, by age group of the index case.
| Duration of Follow-Up | High Vaccine Coverage Cohorts* (Coverage ≥ 30%) | Low Vaccine Coverage Cohorts* (Coverage ≤ 12%) | Vaccine Effectiveness (95% CI; p-Value) | |||
|---|---|---|---|---|---|---|
| Population † | Number of Cases ‡ | Population † | Number of Cases ‡ | Crude | Adjusted £ | |
| Age group: <5 y | ||||||
| 2 y | 1,261 | 0 | 1,814 | 12 | 100% | ** |
| 3 y | 2,985 | 2 | 3,345 | 15 | 85% (35 to 97; 0.0114) | 84% (27 to 96; 0.0175) |
| 4 y | 4,332 | 7 | 5,114 | 18 | 54% (−9 to 81; 0.0801) | 50% (−24 to 80; 0.1380) |
| 5 y | 4,965 | 7 | 5,597 | 18 | 66% (−5 to 82; 0.0638) | 52% (−19 to 80; 0.1153) |
| Age group: ≥5 y | ||||||
| 2 y | 11,737 | 1 | 18,810 | 10 | 84% (−25 to 98; 0.0808) | ** |
| 3 y | 24,467 | 3 | 35,270 | 14 | 69% (−7 to 91; 0.0649) | ** |
| 4 y | 34,428 | 6 | 54,093 | 26 | 64% (12 to 85; 0.0251) | 62% (6 to 85; 0.0361) |
| 5 y | 38,935 | 7 | 59,702 | 26 | 59% (5 to 82; 0.0377) | 59% (1 to 83; 0.0469) |
*The vaccine coverage of individuals living within 25 m of index cases was calculated as the number of two-dose vaccine recipients divided by all population within 25 m.
†Cumulative total population within 25 m of the index cases.
‡Cumulative total cholera cases within 25 m of the index cases (excluding index cases) and within 8–28 d of onset of index cases.
£Adjusted for distance from household to nearest water body for the 3-y analysis, and for age and distance from household to nearest water body for the 4-y and 5-y analyses.
**Not enough cases to develop a multivariable model.