Table 3.

 Comparison of H2 antibody‐positive and negative participants

	Seropositive participants	Seronegative participants	P‐value
No. participants	4	23	–
Smoke or chew tobacco	0	12	0·106
Currently vaccinated for seasonal influenza (2007–2008)	0	7	0·545
Vaccinated for seasonal influenza in last 3 years	1	9	0·758
Reported influenza in last 3 years	2	7	0·582
Exposed to H2‐positive pigs in 2006	1	10	1·0
Mean age*a (years)	53	33	0
Percentage of persons born prior to 1968b (%)	75	22	0·022
Gender ratio (male:female)	4:0	19:4	1·0

*One participant did not provide an age.

^aStatistically significant: t = 4·74, P = 0·00, 95%CI (11·8, 29·9).

^bStatistically significant: Fisher’s exact test P = 0·022.