Table 2

Univariate analysis
Factor	correlation coefficient ρ	p value
Age	-0.431	0.011*
COPD	-0.422	0.011*
Previous vaccination	0.149	0.402
Inhaled steroids	-0.496	0.026*
Smoking	-0.314	0.071
IL-21 at day 28	0.304	0.091

Multivariate analysis
Factor	correlation coefficient β	p value
COPD	-0.558	0.047*

*indicates statistical significance

Table 2: Clinical features associated with post vaccination H1N1 antibody titres.