Table 2.

Pre- and post-vaccination HAI titres and seroprotection and seroconversion rates across frailty strata.

Strain	HAI responses	All (N = 205)	Frail (N = 59)	Pre-frail (N = 85)	Robust (N = 61)	p	p.adj
A/H1N1	Pre- vaccination (Day 0) HAI titer, GMT	15.3 ± 4.7	13.8 ± 4.8	16.8 ± 4.5	14.7 ± 4.9	0.743	0.95
	Pre-vaccination (Day 0) Seroprotection rate, no. (%)	57 (27.8%)	13 (22%)	27 (31.8%)	17 (27.9%)	0.443	0.95
	Post-vaccination (Day 28) HAI titer, GMT	259 ± 4.7	308.9 ± 5.6	265.3 ± 4.4	211.4 ± 4.5	0.403	0.95
	Post-vaccination (Day 28) Seroprotection rate, no. (%)	191 (93.2%)	56 (94.9%)	80 (94.1%)	55 (90.2%)	0.605	0.95
	Post/Pre-vaccination HAI ratio	17 ± 5	22.4 ± 6	15.8 ± 4.7	14.4 ± 4.3	0.277	0.95
	Seroconversion rate, no. (%)	171 (83.4%)	51 (86.4%)	70 (82.4%)	50 (82%)	0.791	0.95
A/H3N2	Pre-vaccination (Day 0) HAI titer, GMT	52.8 ± 5.8	57.9 ± 6.2	52.1 ± 5.7	49.1 ± 5.8	0.873	0.95
	Pre-vaccination (Day 0) Seroprotection rate, no. (%)	111 (54.1%)	30 (50.8%)	51 (60%)	30 (49.2%)	0.378	0.95
	Post-vaccination (Day 28) HAI titer, GMT	1005.1 ± 3.9	1165.2 ± 3.9	890.5 ± 4.3	1031.4 ± 3.4	0.504	0.95
	Post-vaccination (Day 28) Seroprotection rate, no. (%)	199 (97.1%)	58 (98.3%)	81 (95.3%)	60 (98.4%)	0.585	0.95
	Post/Pre-vaccination HAI ratio	19 ± 5.6	20.1 ± 5.4	17.1 ± 5.4	21 ± 6.3	0.745	0.95
	Seroconversion rate, no. (%)	165 (80.5%)	49 (83.1%)	67 (78.8%)	49 (80.3%)	0.836	0.95
B	Pre-vaccination (Day 0) HAI titer, GMT	67.1 ± 4.6	51.5 ± 5	77.1 ± 4.2	71.4 ± 4.6	0.271	0.95
	Pre-vaccination (Day 0) Seroprotection rate, no. (%)	137 (66.8%)	34 (57.6%)	62 (72.9%)	41 (67.2%)	0.154	0.95
	Post-vaccination (Day 28) HAI titer, GMT	1129.5 ± 3.1	1092.3 ± 3.2	1179.8 ± 2.9	1098 ± 3.1	0.897	0.95
	Post-vaccination (Day 28) Seroprotection rate, no. (%)	204 (99.5%)	59 (100%)	85 (100%)	60 (98.4%)	0.585	0.95
	Post/Pre-vaccination HAI ratio	16.8 ± 4.8	21.2 ± 5.3	15.3 ± 4.3	15.4 ± 5.1	0.411	0.95
	Seroconversion rate, no. (%)	166 (81%)	48 (81.4%)	68 (80%)	50 (82%)	0.974	0.95