Table 3.

Model 1.

Variable	Sample size	OR	SE	p	95% CI
Herd size
≥ 250 sows	75	reference
< 250 sows	27	3.86	1.91	< 0.05	1.46	10.19
Distance to nearest pig herd
< 2 miles	40	reference
≥ 2 miles	62	3.42	1.71	< 0.05	1.29	9.12

Multivariable logistic regression model of factors associated with herds that were negative for PRRSV antibodies compared to those seropositive or vaccinated (103 herds in total).

Odds ratio (OR); standard error of the odds ratio (SE); probability function (p); 95% confidence interval (CI) (exp(coefficient+/-(1.96 × standard error)))