HI antibody reactivity of SWs and Cs sera against swine and human influenza viruses during the whole study period (Italy, 2008–2010)^§.

§Values are no. persons with antibodies. ∧Data adjusted by age in binary logistic regression. HI, Haemagglutination inhibition. SWs, swine workers; Cs, controls. OR, odds ratio; CI, confidence interval; nc, not calculated. swH1N1, A/Swine/Italy/44795/08; huH1N1pdm, A/California/7/09; swH1N2, A/Swine/Italy/114347–1/06; huH1N1, A/Brisbane/59/07; swH3N2, A/Swine/Italy/32242/06; huH3N2, A/Uruguay/716/07. Statistically significant values: *, p<0.05; **, p<0.01; ***, p<0.001.