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Table 1 Demography of the study population

From: Influenza and other respiratory viral infections associated with absence from school among schoolchildren in Pittsburgh, Pennsylvania, USA: a cohort study

  Total Grade
K 1 2 3 4 5 6 7 8 9 10 11+
Total study population 2519 314 319 343 355 351 227 275 46 38 88 90 79
Observable for ILI (%)
 Yes 2077 (82) 279 (88) 267 (84) 300 (87) 301 (85) 304 (87) 185 (81) 216 (79) 34 (74) 30 (79) 61 (69) 50 (55) 50 (63)
 No 442 (18) 35 (22) 46 (26) 43 (23) 54 (15) 47 (23) 42 (19) 59 (21) 12 (26) 8 (21) 27 (31) 40 (45) 29 (37)
Observable population
 District
  A 647 54 53 62 56 66 62 69 34 30 61 50 50
  B 1430 225 214 238 245 238 123 147
 School
  A1 204 27 26 32 21 32 30 36
  A2 161 61 50 50
  A3 282 27 27 30 35 34 32 33 34 30
  B1 201 40 40 36 50 35
  B2 270 123 147
  B3 240 47 43 54 41 55
  B4 188 36 34 44 33 41
  B5 342 67 60 59 85 71
  B6 189 35 37 45 36 36
Sex
 Female 995 145 125 149 137 136 91 97 14 17 34 27 23
 Male 1082 134 142 151 164 168 94 119 20 13 27 23 27
Self-reported vaccination §
 No 850 133 111 131 118 122 74 63 17 10 22 25 24
 Yes 694 63 95 105 107 120 66 74 10 8 20 13 13
 Not reported 533 83 61 64 76 62 45 79 7 12 19 12 13
  1. § Of 2077 participants, we obtained a valid immunization response from 1544 children: we failed to interview 296 children regarding their vaccination status; of the children interviewed, 237 did not know their vaccination status or refused to provide a valid answer for any of the times they were questioned