Table 2.

Pre- and post-booster geometric mean concentrations (GMCs) of diphtheria antibodies, including the 95% confidence interval and p value between subgroups.

Predictors		GMCs (IU/mL), (95% CI)
		Pre-Booster	Post-Booster
Sex	Male	0.06 (0.05–0.07)	0.35 (0.26–0.45)
	Female	0.05 (0.04–0.06)	0.26 (0.20–0.34)
	p value	NS	NS
Vaccine	Vacdite	0.06 (0.05–0.07)	0.33 (0.25–0.44)
	Imovax DT Adult	0.05 (0.04–0.05)	0.27 (0.21–0.35)
	p value	NS	NS
Smoker	Yes	0.04 (0.03–0.06)	0.16 (0.08–0.31)
	No	0.05 (0.05–0.06)	0.33 (0.27–0.40)
	p value	NS	0.0125
Needle length (mm)	16	0.05 (0.04–0.06)	0.29 (0.23–0.36)
	25	0.06 (0.05–0.07)	0.33 (0.23–0.47)
	p value	NS	NS
Pre-booster concomitant medication	Yes	0.06 (0.05–0.08)	0.22 (0.16–0.29)
	No	0.05 (0.04–0.05)	0.36 (0.28–0.46)
	p value	NS	0.0142
Related adverse events	Yes	0.04 (0.03–0.05)	0.31 (0.20–0.48)
	No	0.06 (0.05–0.06)	0.29 (0.24–0.37)
	p value	0.0409	NS
Age, median (years)	≤43.3	0.06 (0.05–0.07)	0.49 (0.38–0.64)
	>43.3	0.05 (0.04–0.06)	0.18 (0.14–0.23)
	p value	NS	<0.0001
BMI, median (kg/m2)	≤25.2	0.05 (0.04–0.06)	0.34 (0.26–0.45)
	>25.2	0.05 (0.04–0.06)	0.26 (0.20–0.34)
	p value	NS	NS
Time since last immunisation, median (years)	≤33.9	0.06 (0.05–0.07)	0.46 (0.35–0.59)
	>33.9	0.05 (0.04–0.06)	0.19 (0.15–0.25)
	p value	NS	<0.0001
Pre-vaccination anti-DT GMCs, median (IU/mL)	≤0.05	0.03 (0.02–0.03)	0.18 (0.14–0.24)
	>0.05	0.11 (0.09–0.12)	0.49 (0.39–0.61)
	p value	<0.0001	<0.0001

Note: For abbreviations, see Table 1; NS: not significant; p value calculated with the unpaired t-test.