Table 3.
Participants’ profile for primary analysis period spanning onset of illness from week 45 (8 November 2009) to week 48 (5 December 2009). Values are numbers (column percentages)
| Covariates | Pandemic H1N1 test negative control (n=343) | Pandemic H1N1 test positive case (n=209) | Overall (n=552) |
|---|---|---|---|
| Age category: | |||
| 6 months to 9 years | 71 (21) | 50 (24) | 121 (22) |
| 10-19 years | 56 (16) | 40 (19) | 96 (17) |
| 20-49 years | 148 (43) | 97 (46) | 245 (44) |
| 50-64 years | 47 (14) | 20 (10) | 67 (12) |
| ≥65 years | 21 (6) | 2 (1) | 23 (4) |
| Median (range) age (years) | 27 (<1-88) | 22 (<1-68) | 24 (<1-88) |
| Female sex | 200 (58) | 93 (45) | 293 (53) |
| Chronic conditions | 80 (23) | 35 (17) | 115 (21) |
| Province: | |||
| Alberta | 66 (19) | 30 (14) | 96 (17) |
| British Columbia | 133 (39) | 76 (36) | 209 (38) |
| Ontario | 31 (9) | 2 (1) | 33 (6) |
| Quebec | 113 (33) | 101 (48) | 214 (39) |
| Pandemic H1N1 vaccinated* | 58 (17) | 2 (1) | 60 (11) |
| 2009-10 seasonal vaccine: | |||
| Not vaccinated | 297 (93) | 191 (97) | 488 (94) |
| Vaccinated | 24 (7) | 5 (3) | 29 (6) |
| 2008-9 seasonal vaccine: | |||
| Not vaccinated | 213 (72) | 158 (84) | 371 (77) |
| Vaccinated† | 83 (28) | 29 (16) | 112 (23) |
| Specimen collection interval: | |||
| ≤4 days after illness onset | 297 (87) | 190 (91) | 487 (88) |
| 5-7 days after illness onset | 46 (13) | 19 (9) | 65 (12) |
| Median (range) days | 2 (0-7) | 2 (0-7) | 2 (0-7) |
| Pandemic H1N1 vaccination by age: | |||
| 6 months to 9 years | 22/71 (31) | 1/50 (2) | 23/121 (19) |
| 10-19 years | 3/56 (5) | 0/40 (0) | 3/96 (3) |
| 20-49 years | 21/148 (14) | 1/97 (1) | 22/245 (9) |
| 50-64 years | 11/47 (23) | 0/20 (0) | 11/67 (16) |
| ≥65 years | 1/21 (5) | 0/2 (0) | 1/23 (4) |
| Chronic conditions by age: | |||
| 6 months to 9 years | 11/71 (15) | 6/50 (12) | 17/121 (14) |
| 10-19 years | 8/56 (14) | 9/40 (23) | 17/96 (18) |
| 20-49 years | 29/148 (20) | 12/97 (12) | 41/245 (17) |
| 50-64 years | 18/47 (38) | 7/20 (35) | 25/67 (37) |
| ≥65 years | 14/21 (67) | 1/2 (50) | 15/23 (65) |
| With chronic conditions: | |||
| Not pandemic H1N1 vaccinated | 59 (74) | 34 (97) | 93 (81) |
| Pandemic H1N1 vaccinated | 21 (26) | 1 (3) | 22 (19) |
| Without chronic conditions: | |||
| Not pandemic H1N1 vaccinated | 226 (86) | 173 (99) | 399 (91) |
| Pandemic H1N1 vaccinated | 37 (14) | 1 (1) | 38 (9) |
| Interval to specimen collection ≤4 days: | |||
| Not pandemic H1N1 vaccinated | 251 (85) | 188 (99) | 439 (90) |
| Pandemic H1N1 vaccinated | 46 (15) | 2 (1) | 48 (10) |
| Interval to specimen collection 5-7 days: | |||
| Not pandemic H1N1 vaccinated | 34 (74) | 19 (100) | 53 (82) |
| Pandemic H1N1 vaccinated | 12 (26) | 0 (0) | 12 (18) |
*Received vaccine ≥2 weeks before onset of illness; excludes from numerator and denominator those immunised <2 weeks before onset.
†Excludes children too young to have received 2008-9 seasonal vaccine.