Table 2.

Specific anti-PPS IgG antibody levels in young and elderly.

Pre-immune serum GMC (95% CI)
		CPS	CPS + 22F	P value
PPS4	Young	1.5 (0.59–2.41)	1.22 (0.77–1.66)	0.033
	Elderly	1.94 (0.85–3.03)	1.39 (0.97–1.81)	0.008
PPS14	Young	3.86 (2.54–5.18)	4.02 (2.10–5.94)	0.370
	Elderly	4.77 (1.61–7.93)	4.73 (2.42–7.04)	0.367
Post-immune serum GMC (95% CI)
		CPS	CPS + 22F	P value
PPS4	Young	4.03 (1.68–6.38)	3.45 (1.62–5.28)	0.036
	Elderly	3.95 (0.73–7.17)	3.50 (1.01–5.99)	0.142
PPS14	Young	18.41 (7.24–29.58)	18.43 (8.46–28.40)	0.708
	Elderly	11.43 (4.44–18.42)	10.22 (3.35–17.09)	0.013

Geometric mean concentration (GMC, μg/ml) of specific anti-PPS IgG antibody in pre-and post-immunization serum from young and elderly volunteers by two ELISA methods. CPS – serum adsorbed with CPS prior to ELISA. CPS+22F – serum absorbed with PPS22F and CPS prior to ELISA. P values shown in bold indicate significant difference between absorption methods by two tailed paired Student's T-test.