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Table 5 Univariate and multivariable analysis of risk factors associated with clinical malaria infections

From: A cluster randomised controlled trial of two rounds of mass drug administration in Zanzibar, a malaria pre-elimination setting—high coverage and safety, but no significant impact on transmission

  Intervention shehias Control shehias
Survey population (n; %)1 Malaria cases (n; %)2 OR (CI95%) aOR3(CI95%) p value Survey population
(n; %)1
Malaria cases (n; %)2 OR (CI95%) aOR3 (CI95%) p value
Residing in households sprayed in the last 12 months
 No 1316; 12.5 18; 23.4 1 (Ref) 1 (Ref) 1437; 12.3 24; 18.1 1 (Ref) 1 (Ref)
 Yes 9218; 87.5 59; 76.6 0.4; 0.3–0.7 0.5; 0.2–0.9 0.018 10,205; 87.7 109; 82.0 0.6; 0.4–0.9 0.6; 0.4–1.0 0.074
Residing in household with at least one mosquito net
 No 1283; 12.2 9; 11.7 1 (Ref) 1 (Ref) 1739; 14.9 16; 12.0 1 (Ref) 1 (Ref)
 Yes 9251; 87.8 68; 88.3 1.0; 0.5–2.0 2.8; 0.9–9.1 0.085 9903; 85.1 117; 88.0 1.3; 0.8–2.2 2.6; 1.2–5.5 0.015
Residing in households with at least one mosquito net and/or sprayed in the past 12 months
 No 293; 2.8 6; 7.8 1 (Ref) 1 (Ref) 200; 1.7 3; 2.3 1 (Ref) 1 (Ref)
 Yes 10,241; 97.2 71; 92.2 0.3; 0.1–0.7 0.4; 0.1–1.9 0.262 11,442; 98.3 130; 97.7 0.7; 0.2–2.0 0.5; 0.1–2.1 0.356
Age
 < 5 years 1622; 15.4 4; 5.2 1 (Ref) 1 (Ref) 1785; 15.3 10; 7.5 1 (Ref) 1 (Ref)
 5–14 years 2725; 25.9 22; 28.6 3.3; 1.1–9.4 3.7; 1.2–11.1 0.019 3104; 26.7 30; 22.6 1.7; 0.8–3.6 2.1; 1.0–4.4 0.064
 15–24 years 1895; 18.0 27; 35.1 5.7; 2.0–16.4 4.4; 1.5–13.1 0.009 2034; 17.5 42; 31.6 3.8; 1.8–7.7 3.7; 1.7–8.0 0.001
 > 25 years 4292; 40.7 24; 31.2 2.2; 0.8–6.4 1.4; 0.5–4.3 0.510 4719; 40.5 51; 38.4 1.9; 1.0–3.8 1.6; 0.8–3.2 0.228
Sex
 Female 5440; 51.6 26; 33.8 1 (Ref) 1 (Ref) 6028; 51.8 50; 37.6 1 (Ref) 1 (Ref)
 Male 5094; 48.4 51; 66.2 2.1; 1.3–3.4 2.0; 1.2–3.2 0.009 5614; 48.2 83; 62.4 1.8; 1.3–2.6 1.7; 1.1–2.5 0.009
Travel in last month
 No travel 10,152; 96.4 54; 70.1 1 (Ref) 1 (Ref) 11,262; 96.7 95; 71.4 1 (Ref) 1 (Ref)
 Within Zanzibar 336; 3.2 3; 3.9 1.7; 0.5–5.3 2.3; 0.7–7.6 0.160 325; 2.8 3; 2.3 1.1; 0.3–3.4 1.1; 0.3–3.7 0.838
 Outside of Zanzibar 43; 0.4 20; 26.0 87.5; 46.4–165.1 103.4; 49.8–214.9 < 0.001 55; 0.5 35; 26.3 75.8; 42.3–136.0 85.0; 4.2–159.8 < 0.001
Reported use of a mosquito net the previous night
 No 2606; 24.7 29; 37.7 1 (Ref) 1 (Ref) 3430; 29.5 45; 33.8 1 (Ref) 1 (Ref)
 Yes 7928; 75.3 48; 62.3 0.5; 0.3–0.8 0.5; 0.3–1.0 0.033 8212; 70.5 88; 66.2 0.8; 0.6–1.2 0.7; 0.5–1.1 0.167
  1. 1Healthy individuals at study baseline: N(Intervention shehias) = 10,534; N(Control shehias) = 11,642; 194 (0.9%) individuals excluded due to missing data, and 126 (0.6%) excluded for being positive for malaria by PCR
  2. 2Malaria cases diagnosed at health facilities during the study period May 2016–August 2017: N(Intervention shehias) = 77; N(Control shehias) = 133; 141 (40.2%) individuals excluded due to missing data
  3. 3All variables were included in the model of adjusted OR; significant p values are presented in italics