TABLE 1

Demographic Characteristics of the Enrolled Study Population Over 5 Influenza Seasons (November–April) Overall and Among Those Who Had Study-Confirmed Influenza Infection

CharacteristicsInpatientOutpatient
Total Nn Influenza + (row %)RRaP ValueTotal Nn Influenza + (row %)RRaP Value
Age.74<.001
 0–<6 mo142396 (6.7)1.00105952 (4.9)1.00
 6mo–<2y97069 (7.1)1.052556253 (9.9)2.02
 2y–<5y57734 (5.9)0.872003311 (15.5)3.16
Race/ethnicityb.11<.001
 Non-Hispanic white121669 (5.7)1.001560133 (8.5)1.00
 Non-Hispanic black95169 (7.3)1.282615330 (12.6)1.48
 Hispanic52635 (6.7)1.17977107 (11.0)1.28
 Other27324 (8.8)1.5545646 (10.1)1.18
Site<.001.04
 Nashville1271103 (8.1)2.611878218 (11.6)1.24
 Rochester102375 (7.3)2.362038239 (11.7)1.26
 Cincinnatic67621 (3.1)1.001702159 (9.3)1.00
Insuranced.008.09
 Public1848135 (7.3)1.354239486 (11.5)1.25
 Private97953 (5.4)1.001112102 (9.2)1.00
 None13310 (7.5)1.3924425 (10.2)1.12
Vaccination statuse.003<.001
 Full33214 (4.2)1.0086482 (9.5)1.00
 Partial29319 (6.5)1.5499697 (9.7)1.03
 None81572 (8.8)2.102619377 (14.4)1.52
High riskf.08.23
 Yes91350 (5.5)0.761278152 (11.9)1.11
 Yes, asthma62725 (4.0)0.551126125 (11.1)1.04
 No2057149 (7.2)1.004340464 (10.7)1.00
Symptom daysg<.001<.001
 ≤277385 (11.0)2.11573201 (35.1)4.36
 >22190114 (5.2)1.005033405 (8.0)1.00
  • a Relative risk (RR) is calculated by dividing the percentage who are influenza-positive in each category by the percentage who are influenza-positive in the reference category, denoted by RR = 1.00.

  • b Race/ethnicity was missing for 14 children.

  • c Inpatient data for Cincinnati includes 2 seasons (2004–2005 and 2008–2009).

  • d Insurance status was missing for 33 children.

  • e Vaccination status determined by provider confirmation for children 6 to 59 months of age.

  • f The P values for high-risk compare yes/no responses, excluding yes asthma, by influenza status.

  • g Symptom days were missing for 7 influenza-negative inpatients and for 2 influenza-negative outpatients.