. 2002 Aug;8(8):814–819. doi: 10.3201/eid0808.010474

Table 3. Variables associated with seropositivity to swine influenza viruses among the farm participants and the statistical strength of these associations ^a.

Variable	HI titer >40^b	HI titer >80^b
Being a farm owner	p=0.04	p=0.02
Being a farm owner or the family member of a farm owner	p=0.03	p=0.02
Living on a swine farm	(p = 0.07)	p=0.04
Going into a swine barn >4 days/week	(p = 0.12)	p=0.04
Age >50 yrs	p=0.02	p=0.03
Having received the swine flu vaccine in 1976–77	p=0.02	(p = 0.44)
Ever having received any influenza virus vaccine	p=0.03	(p = 0.19)

^aP values determined by chi-square or two-sided Fisher’s exact analyses; p values >0.05 cut-off for significance are shown in parentheses. ^bTo either swine virus. Abbreviation used: HI, hemagglutination-inhibition.

Table 3. Variables associated with seropositivity to swine influenza viruses among the farm participants and the statistical strength of these associations a.

Table 3. Variables associated with seropositivity to swine influenza viruses among the farm participants and the statistical strength of these associations ^a.