Table 3.

Multivariable associations between malaria exposure in the first 6 months and incidence of malaria after 6 months of age

	Any malaria incidence		Clinical malaria incidence
	Adjusted IRR (95% CI)	P-value	Adjusted IRR (95% CI)	P-value
Any malaria exposure
Any malaria
None	REF	0.009	REF	< 0.0001
Malaria	1.27 (1.06–1.52)		1.76 (1.42–2.19)
Study site
Liwonde	REF	< 0.0001	REF	< 0.0001
Mfera	3.52 (2.83–3.90)		6.98 (5.37–9.08)
Season of birth
Dry	REF	0.03	REF	0.0002
Rainy	0.84 (0.71–0.99)		0.72 (0.57–0.92)
Maternal age
Per unit increase	0.94 (0.92–0.96)	< 0.0001	0.92 (0.90–0.95)	< 0.0001
Gravidity
Per unit increase	1.13 (1.05–1.20)	< .0.0001	1.13 (1.04–1.22)	0.005
Asymptomatic P. falciparum exposure
Asymp. Pf infection
None	REF	< 0.0001	REF	0.002
Pf infection	1.53 (1.26–1.85)		1.56 (1.18–2.07)
Study site
Liwonde	REF	< 0.0001	REF	< 0.0001
Mfera	3.24 (2.71–3.89)		7.41 (5.44–10.07)
Season of birth
Dry	REF	0.001	REF	0.0004
Rainy	0.71 (0.58–0.87)		0.55 (0.40–0.77)
Maternal age
Per unit increase	0.95 (0.93–0.97)	< 0.0001	0.92 (0.89–0.95)	< 0.0001
Gravidity
Per unit increase	1.13 (1.05–1.22)	0.001	1.19 (1.07–1.31)	0.0009
Clinical malaria exposure
Clinical malaria
None	REF	< 0.0001	REF	< 0.0001
Clinical malaria	1.64 (1.38–1.94)		1.85 (1.48–2.32)
Study site
Liwonde	REF	< 0.0001	REF	< 0.0001
Mfera	3.19 (2.71–3.75)		6.58 (5.04–8.60)
Season of birth
Dry	REF	0.02	REF	0.002
Rainy	0.83 (0.70–0.97)		0.69 (0.54–0.87)
Maternal age
Per unit increase	0.95 (0.93–0.96)	< 0.0001	0.93 (0.90–0.95)	< 0.0001
Gravidity
Per unit increase	1.11 (1.05–1.18)	0.0005	1.12 (1.03–1.22)	0.006

^aPoisson regression