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Table 2 Incidence of CHIKF among children < 16 years in Ngerenya and Pingilikani

From: Endemic chikungunya fever in Kenyan children: a prospective cohort study

  Ngerenya
(N = 73,028 pyo)
Pingilikani
(N = 63,481 pyo)
  Incidence (95% CI) IRRs (95% CI) Incidence (95% CI) IRRs (95% CI)
Overall incidence 336 (296,381) 288 (248,333)
Year
 2014 536 (418,676) Ref
 2015 79 (41,138) Ref 348 (255,464) 0.65 (0.45, 0.94)
 2016 920 (774,1086) 11.58 (6.42, 20.89) 274 (192,380) 0.51 (0.34, 0.77)
 2017 514 (406,642) 6.47 (3.52, 11.88) 122 (69,198) 0.23 (0.13, 0.39)
 2018 127 (72,207) 1.60 (0.76, 3.39) 129 (70,216) 0.24 (0.14, 0.43)
Sex
 Female 320 (265,384) Ref 331 (270,401) Ref
 Male 352 (294,418) 1.10 (0.86, 1.41) 245 (194,306) 0.74 (0.55, 0.99)
Age (years)
 < 1 1363 (1030,1770) Ref 979 (674,1375) Ref
 1 to < 5 658 (549,783) 0.48 (0.35, 0.66) 509 (406,629) 0.52 (0.35, 0.78)
 5 to < 10 221 (166,288) 0.16 (0.11, 0.24) 208 (151,280) 0.21 (0.14, 0.33)
 10 to 15 35 (16,67) 0.03 (0.01, 0.05) 93 (58,143) 0.10 (0.06, 0.17)
Distance from dispensary (Km)
 < 1 881 (599,1251) Ref 1037 (677,1519) Ref
 1 to < 2 636 (483,822) 0.72 (0.47, 1.12) 855 (605,1173) 0.82 (0.50, 1.36)
 2 to < 3 456 (353,580) 0.52 (0.34, 0.79) 883 (700,1099) 0.85 (0.55, 1.33)
 3 to < 4 376 (277,498) 0.43 (0.27, 0.67) 207 (116,343) 0.20 (0.11, 0.38)
 4 to < 5 181 (120,261) 0.21 (0.12, 0.34) 148 (81,249) 0.14 (0.07, 0.27)
 5 to < 6 84 (47,139) 0.10 (0.05, 0.18) 32 (15,59) 0.03 (0.02, 0.06)
Season
 Jan - Mar 459 (368,566) Ref 273 (199,365) Ref
 Apr - Jun 350 (271,445) 0.76 (0.55, 1.05) 433 (338,546) 1.59 (1.09, 2.30)
 Jul - Sep 276 (206,362) 0.60 (0.43, 0.85) 281 (205,374) 1.03 (0.68, 1.55)
 Oct - Dec 249 (179,338) 0.54 (0.37, 0.79) 147 (91,225) 0.54 (0.32, 0.91)
  1. *Ref – comparator group
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