highly significantp = 0.006
When the farm was controlled as a confounding effect by using a multivariable model, the effect of the vaccine was more pronounced, although still not significant when analyzing all four farms together ( p = 0.094, OR = 0.62 95%CI: 0.36–1.08), and highly significant for farms 1–3 ( p = 0.006, OR = 0.32, 95% CI: 0.14–0.72).