Despite elevated titers , among the 187 study subjects for whom we had complete follow - up , participants working at swine CAFOs had significantly greater odds of seroconverting against both the swine H1N1 ( odds ratio [ OR ] 19 . 16 , 95 % confidence interval [ CI ] 3 . 55 - 358 . 65 ) and swine H3N2 ( OR 2 .