| Exposure level | Total no. of flocks | No. of positive flocks | Incidence | IRR |
---|---|---|---|---|---|
 |  |  | (new cases per 1000 farms) | (95%CI) | |
Categorization of the number of vets or retailers who had bought the vaccine | 1 (0-1vet or retailer) | 71 216 | 47 | 0.66 | Referent |
2 (>1 vet or retailer) | 7247 | 10 | 1.4 | 2.1 (1.1-4.1) | |
Categorization of the number of farms that had bought the vaccine | 1 (0–4 farms) | 49 849 | 25 | 0.50 (*) | Referent |
 | 2 (5–10 farms) | 20 821 | 17 | 0.82 (*) | 1.6 (0.88-3.0) |
 | 3 (>10 farms) | 7793 | 15 | 1.9 (*) | 3.8 (2.0-7.3) |
Herd size (median for each province) | Â | 78 463 | 57 | Â | 1.005 |
 |  |  |  |  | (1.001-1.01) |