Differential impact of malaria control interventions on P. falciparum and P. vivax infections in young Papua New Guinean children

Table 2 Multivariate predictors of molecularly determined new P. falciparum and P. vivax blood-stage infections in 2013

	P. falciparum				P. vivax
	IR	IRR	CI₉₅	p	IR	IRR	CI₉₅	p
Areas of residence
Ilahita 1–4, 6,7	1.09	Reference group			0.65	Reference group
Balanga and Balif	1.25	1.22	0.70–2.12	0.485	0.94	1.46	0.81–2.64	0.213
Kamanokor and Ilahita 5	1.82	1.61	0.92–2.80	0.096	4.83	6.66	4.24–10.5	< 0.001
Sunuhu 1 and 2	3.57	3.10	2.08–4.63	< 0.001	5.37	8.16	5.38–12.4	< 0.001
			p < 0.0001^a				p < 0.0001^a
Age						1.26	1.13–1.40	< 0.001
ADI visit interval
Enrolment–week 4	1.23	Reference group			3.20	Reference group
Week 4–week 8	0.85	0.58	0.27–1.23	0.153	2.62	0.71	0.52–0.98	0.035
Week 8–week 12	0.22	0.15	0.06–0.38	< 0.001	1.60	0.44	0.30–0.63	< 0.001
Week 12–week 16	0.77	0.50	0.23–1.09	0.081	2.30	0.59	0.43–0.82	< 0.001
Week 16–week 20	1.23				3.20	0.87	0.60–1.25	0.446
Week 20–week 24	2.58	1.99	1.00–3.96	0.049	3.60
Week 24–week 28	1.17	0.83	0.43–1.61	0.583	2.20	0.57	0.41–0.79	< 0.001
Week 28–week 32	1.13	0.84	0.43–1.64	0.602	1.98	0.48	0.34–0.69	< 0.001
Week 32–week 36	1.28	0.89	0.49–1.64	0.719	2.46	0.58	0.42–0.80	< 0.001
Week 36–week 40	7.19	5.55	3.33–9.25	< 0.001	2.26	0.56	0.39–0.79	< 0.001
			p < 0.0001^a				p < 0.0001^a
Recent antimalarial use^b	8.50	10.4	5.92–18.2	< 0.001	2.79
Febrile illness	2.05				3.02
2 weeks history of febrile illness^c	2.11				2.31
Haemoglobin
≥ 10 g/dL	1.60				2.15
9–9.9 g/dL	1.88				2.48
≤ 9 g/dL	2.06				2.87

Estimates from a multivariate negative binomial regression with GEE model predicting risk of acquiring new species-specific clones for P. falciparum and P. vivax in a 4-week interval when the child was considered at risk. A backward selection approach was used with the best fitting model consisting of the significant associations. IR incidence rate, IRR incidence rate ratio, CI₉₅ 95% confidence interval, p p value, g/dL grams/decilitre, ADI active detection of infections. ^aOverall significance level for the variable estimated using Wald chi-square test. ^bAntimalarial treatment within 28 days before the start of the interval. ^cExcluding febrile illness at the time of visit

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