Table 1. Regression analysis for factors which may influence the geometric mean of the fold increase in antibody titre after first infection.

Explanatory variable	N	Fold increase in geometric mean and its ratio
		Adjusted GMa [95% CI]	Ratio [95% CI]
Response to BK-SE36 vaccination (based on ≥1.92-fold increase at Day 42)
Responder	11	3.3 [2.1, 5.3]	2.3 [1.3, 3.8]	1.5 [0.9, 2.6]
Non responder	26	2.2 [1.6, 3.0]	1.5 [1.0, 2.2]	1.0
Placebo, Control	40	1.5 [1.2, 1.9]	1.0
p-value		0.005
Age (yr)
6–10	30	2.5 [1.9, 3.5]	1.0
11–20	47	1.9 [1.5, 2.5]	0.8 [0.5, 1.13]
p-value		0.175
Anti-SE36 antibody titre before first infection
≤52	44	2.5 [2.0, 3.2]	1.0
>52	33	1.9 [1.4, 2.7]	0.8 [0.5, 1.1]
p-value		0.156
Parasitemia during the first infection (parasites/μl)
<5,000	41	1.9 [1.4, 2.5]	1.0
≥5,000	36	2.6 [2.0, 3.4]	1.4 [0.9, 2.0]
p-value		0.091

Significant results are shown in bold. N, sample size; GM, geometric mean; CI, confidence interval.

^aAll variables shown in the table are adjusted simultaneously using the multivariate linear regression. The p-value refers to the significance of the effect of the regression variable in the model.