Table 3.
Natural transmission studies included in the meta-analysis.
| Database # | Authors | Location | BCG source | BCG route | BCG dose | Controls_n | Vaccinates_n | Reported efficacy |
|---|---|---|---|---|---|---|---|---|
| 579 | Ameni et al. (35) | Ethiopia | BCG Danish 1331 | Subcutaneous | 1–4 × 106 CFU | 26 | 23 | 30% |
| 1266 | Ameni et al. (23) | Ethiopia | BCG Danish 1331 | Subcutaneous | 1 × 106 CFU | 14 | 13 | 60% |
| 1358 | Nugent et al. (34) | New Zealand | BCG Danish 1331 | Oral and Subcutaneous | 1 × 108 CFU | 531 | 644 | 67% |
| 1373 | Lopez-Valencia et al. (25) | Mexico | BCG Tokyo | Subcutaneous | 1 × 106 CFU | 66 | 65 | 60% |
| 1410 | Nugent et al. (36) | New Zealand | BCG Danish 1331 | Subcutaneous | 3 × 105 CFU | 297 | 520 | 85% |
The studies conducted in Ethiopia by Ameni et al. (23, 35) used a reactor to sentinel ratio of >1. Nugent et al. (34) included 1,286 free-ranging cattle (676 vaccinates and 531 naïve controls) stocked at low densities, and challenged with a low force of infection, mimicking a more representative field setting. This was followed up with a subsequent field study (36) conducted in ~800 free-ranging cattle that were followed up for over 3 years and similarly showed a relatively high overall protective efficacy of ~85%. Lopez-Valencia et al. (25) did not conduct necropsy.