An average of 8.4 clinical vivax malaria...

An average of 8.4 clinical vivax malaria episodes per 100 person-months at risk were recorded in the study population over the study period, with a peak of 39.3 cases per 100 person-months in October 2011 (Supplementary Figure 4). A total of 529 clinical vivax malaria episodes were recorded over the whole study period. Survival analysis showed no delay in time to the first clinical vivax malaria episode in the upper and middle terciles of IgG response to any PvDBP variant or MSP, compared with the lower tercile of antibody response (Supplementary Figure 5). We compared HRs for the time to the first clinical vivax malaria episode across terciles of specific antibody levels, using Cox proportional hazards models adjusted for age, sex, and DARC genotype, and found no significant association between levels of specific IgG antibodies and prospective risk of clinical vivax malaria (Table 2).

Antigen	Variant	Middle vs Lower Tercile of Reactivity Indices^a	Upper vs Lower Tercile of Reactivity Indices^a
PvDBP	Sal I	1.05 (.73–1.51)	.78	1.14 (.78–1.67)	.49
AH	0.88 (.62–1.25)	.47	0.88 (.60–1.27)	.49
C	0.91 (.64–1.29)	.60	0.97 (.67–1.40)	.89
O	0.83 (.59–1.16)	.28	0.89 (.61–1.26)	.48
P	0.81 (.56–1.15)	.25	0.93 (.64–1.34)	.69
PvMSP-1₁₉	Belém	0.82 (.58–1.16)	.26	1.20 (.85–1.68)	.31
PvMSP-3α	Belém	1.11 (.76–1.61)	.60	1.21 (.83–1.77)	.33
PvMSP-9	Belém	0.86 (.60–1.24)	.42	1.01 (.72–1.43)	.93

Antigen	Variant	Middle vs Lower Tercile of Reactivity Indices^a	Upper vs Lower Tercile of Reactivity Indices^a
PvDBP	Sal I	1.05 (.73–1.51)	.78	1.14 (.78–1.67)	.49
AH	0.88 (.62–1.25)	.47	0.88 (.60–1.27)	.49
C	0.91 (.64–1.29)	.60	0.97 (.67–1.40)	.89
O	0.83 (.59–1.16)	.28	0.89 (.61–1.26)	.48
P	0.81 (.56–1.15)	.25	0.93 (.64–1.34)	.69
PvMSP-1₁₉	Belém	0.82 (.58–1.16)	.26	1.20 (.85–1.68)	.31
PvMSP-3α	Belém	1.11 (.76–1.61)	.60	1.21 (.83–1.77)	.33
PvMSP-9	Belém	0.86 (.60–1.24)	.42	1.01 (.72–1.43)	.93

Table 2.

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Association Between Levels of Naturally Acquired Antibodies to PvDBP and PvMSP Variants and Prospective Risk of Clinical Vivax Malaria in Rural Amazonians

Antigen	Variant	Middle vs Lower Tercile of Reactivity Indices^a		Upper vs Lower Tercile of Reactivity Indices^a
Antigen	Variant	HR (95% CI)^b	P Value	HR (95% CI)^b	P Value
PvDBP	Sal I	1.05 (.73–1.51)	.78	1.14 (.78–1.67)	.49
	AH	0.88 (.62–1.25)	.47	0.88 (.60–1.27)	.49
	C	0.91 (.64–1.29)	.60	0.97 (.67–1.40)	.89
	O	0.83 (.59–1.16)	.28	0.89 (.61–1.26)	.48
	P	0.81 (.56–1.15)	.25	0.93 (.64–1.34)	.69
PvMSP-1₁₉	Belém	0.82 (.58–1.16)	.26	1.20 (.85–1.68)	.31
PvMSP-3α	Belém	1.11 (.76–1.61)	.60	1.21 (.83–1.77)	.33
PvMSP-9	Belém	0.86 (.60–1.24)	.42	1.01 (.72–1.43)	.93

Antigen	Variant	Middle vs Lower Tercile of Reactivity Indices^a		Upper vs Lower Tercile of Reactivity Indices^a
Antigen	Variant	HR (95% CI)^b	P Value	HR (95% CI)^b	P Value
PvDBP	Sal I	1.05 (.73–1.51)	.78	1.14 (.78–1.67)	.49
	AH	0.88 (.62–1.25)	.47	0.88 (.60–1.27)	.49
	C	0.91 (.64–1.29)	.60	0.97 (.67–1.40)	.89
	O	0.83 (.59–1.16)	.28	0.89 (.61–1.26)	.48
	P	0.81 (.56–1.15)	.25	0.93 (.64–1.34)	.69
PvMSP-1₁₉	Belém	0.82 (.58–1.16)	.26	1.20 (.85–1.68)	.31
PvMSP-3α	Belém	1.11 (.76–1.61)	.60	1.21 (.83–1.77)	.33
PvMSP-9	Belém	0.86 (.60–1.24)	.42	1.01 (.72–1.43)	.93

Abbreviations: CI, confidence interval; HR, hazard ratio; PvDBP, Plasmodium vivax Duffy binding protein; P. vivax PvMSP, merozoite surface protein.

^a Antibody levels were stratified into terciles of reactivity indices for analysis.

^b HRs were obtained with Cox proportional hazards models adjusted for age, sex, and genotype for the Duffy antigen/receptor for chemokines.

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