Table 2. Overview of the microarray data, stratified by age, cut-off for seropositivity, and study period (pre- versus post-pandemic).

	A/2009 (H1N1) Microarray Titer	Age Group (years)
		5–9	10–19	20–44	45–64
Pre-pandemic	>20	0	0·30	0·60	0·55
	>40	0	0·23	0·33	0·37
	>65	0	0·13	0·22	0·30
Post-pandemic	>20	0·64	0·53	0·54	0·59
	>40	0·64	0·43	0·42	0·36
	>65	0·64	0·43	0·25	0·22
	>20	0·64	0·24	−0·05	0·04
Post-Pre	>40	0·64	0·20	0·10	−0·01
	>65	0·64	0·30	0·03	−0·08

For each group the seroprevalence, i.e. the fraction with a titer higher than the cut-off, is shown. Also shown are the seroprevalence differences between the post-and pre-pandemic samples.