Table 1.
Study Population Characteristics By Vaccination Status
| Characteristic | Children by 2015–2016 Influenza Vaccine Status, No. (%) | P Valuea | ||
|---|---|---|---|---|
| Unvaccinated (n = 594) | LAIV (n = 101) | IIV (n = 317) | ||
| RT-PCR influenza status | ||||
| Influenza A positive | 17 (103) | 13 (13) | 8 (25) | < .001 |
| Influenza B positive | 12 (70) | 9 (9) | 6 (19) | |
| Influenza negative | 71 (421) | 78 (79) | 86 (273) | |
| Children testing positive to noninfluenza viruses among the test-negative controls | 43 (180/421) | 44 (35/79) | 51 (139/273) | .10 |
| Age range | ||||
| 2–4 y | 28 (166) | 33 (33) | 36 (114) | < .01 |
| 5–8 y | 36 (215) | 47 (48) | 36 (113) | |
| 9–17 y | 36 (213) | 20 (20) | 28 (90) | |
| Female sex | 46 (273) | 54 (55) | 44 (139) | .17 |
| Race/ethnicity | ||||
| Non-Hispanic white | 60 (356) | 61 (62) | 65 (207) | .05 |
| Non-Hispanic black | 16 (98) | 10 (10) | 16 (51) | |
| Hispanic white | 19 (111) | 20 (20) | 12 (38) | |
| Other | 5 (29) | 9 (9) | 7 (21) | |
| Enrollment site | ||||
| Florida | 1 (4) | 2 (2) | <1 (1) | < .001 |
| Minnesota | 2 (13) | 2 (2) | 1 (3) | |
| North Carolina | 17 (99) | 2 (2) | 8 (25) | |
| Ohio | 4 (24) | 9 (9) | 2 (5) | |
| Oregon | 2 (10) | 4 (4) | 1 (9) | |
| Tennessee | 11 (63) | 35 (35) | 28 (87) | |
| Texas | 38 (224) | 32 (32) | 28 (88) | |
| Wisconsin | 26 (157) | 15 (15) | 31 (99) | |
| Enrollment period | ||||
| 3–30 January | 18 (105) | 12 (12) | 15 (47) | .25 |
| 31 January to 27 February | 36 (216) | 35 (35) | 31 (99) | |
| 28 February to 26 March | 36 (213) | 40 (40) | 40 (128) | |
| 27 March to 15 April | 10 (60) | 14 (14) | 14 (43) | |
| Presence of high-risk conditions for influenza | 16 (93) | 6 (6) | 26 (81) | < .001 |
| Privately insured | 45 (265) | 56 (57) | 53 (168) | .01 |
| Fully vaccinated in 2015–2016 | … | 96 (97) | 95 (301) | … |
| No. of outpatient visits in past 6 mo | ||||
| ≤1 | 57 (337) | 41 (41) | 42 (132) | < .001 |
| ≥2 | 43 (257) | 59 (60) | 58 (185) | |
| Reported symptoms | ||||
| Fever | 100 (594) | 100 (101) | 100 (317) | >.99 |
| Cough | 85 (507) | 81 (82) | 83 (264) | .48 |
| Sore throat | 74 (439) | 74 (75) | 62 (198) | .001 |
| Runny or stuffy nose | 81 (481) | 74 (75) | 83 (262) | .17 |
| Headaches | 59 (350) | 47 (47) | 51 (163) | .02 |
| Body aches | 45 (266) | 38 (38) | 39 (124) | .16 |
| Irritability | 59 (349) | 57 (58) | 56 (178) | .75 |
| Fatigue/run down | 88 (520) | 81 (82) | 89 (282) | .12 |
| Nausea | 35 (208) | 37 (37) | 38 (120) | .69 |
| Vomiting | 28 (169) | 19 (19) | 24 (77) | .08 |
| Diarrhea | 15 (87) | 7 (7) | 13 (41) | .10 |
| Time since symptom onset <2 d | 31 (183) | 35 (35) | 39 (123) | < .05 |
Abbreviations: IIV, inactivated influenza vaccine; LAIV, live attenuated influenza vaccine; RT-PCR, reverse-transcriptase polymerase chain reaction.
a
P value from tests comparing distributions between unvaccinated children, LAIV recipients, and IIV recipients.