Table 2.
Characteristics of mild and severe cases of influenza-like illness (ILI) and controls for three influenza seasons (2003–2004; 2004–2005; 2009 H1N1) in Massachusetts
| Severe ILI | Mild ILI | Controls | |
|---|---|---|---|
| 2003–2004 | n = 202 | n = 2194 | n = 8929 |
| Age–Mean ± SD | 68 ± 16 | 52 ± 18 | 51 ± 15 |
| Age–Median | 72 | 52 | 51 |
| BMI–Mean ± SD | 29 ± 6·3 | 28 ± 6·0 | 28 ± 5·7 |
| BMI–Median | 28 | 27 | 27 |
| No. (%) | No. (%) | No. (%) | |
| Normal weight | 58 (29) | 745 (34) | 3057 (34) |
| Overweight | 71 (35) | 757 (35) | 3234 (36) |
| Obese | 73 (36) | 692 (32) | 2638 (30) |
| Female | 103 (51) | 1514 (69) | 5687 (64) |
| Charlson score | |||
| 0 | 81 (40) | 1476 (67) | 7064 (79) |
| 1 | 32 (16) | 404 (18) | 1083 (12) |
| ≥2 | 89 (44) | 314 (14) | 782 (8·8) |
| Vaccinated* | 80 (40) | 641 (29) | 2202 (25) |
| Race | |||
| White | 12 (5·9) | 364 (17) | 1580 (18) |
| Black | 5 (2·5) | 93 (4·2) | 324 (3·6) |
| Asian | 1 (0·50) | 24 (1·1) | 81 (0·91) |
| Other | 0 | 2 (<0·10) | 9 (<0·10) |
| Unknown/missing | 184 (91) | 1711 (78) | 6935 (78) |
| 2004–2005 | n = 204 | n = 2614 | n = 10 117 |
| Age–Mean (SD) | 69 ± 14 | 54 ± 17 | 52 ± 16 |
| Age–Median | 72 | 54 | 51 |
| BMI–Mean (SD) | 29 ± 6·4 | 29 ± 6·3 | 28 ± 5·7 |
| BMI–Median | 28 | 28 | 27 |
| No. (%) | No. (%) | No. (%) | |
| Normal weight | 53 (26) | 803 (31) | 3487 (34) |
| Overweight | 77 (38) | 891 (34) | 3625 (36) |
| Obese | 74 (36) | 920 (35) | 3005 (30) |
| Female | 120 (59) | 1719 (66) | 6313 (62) |
| Charlson score | |||
| 0 | 77 (38) | 1628 (62) | 7686 (76) |
| 1 | 45 (22) | 564 (22) | 1438 (14) |
| ≥2 | 82 (40) | 422 (16) | 993 (9·8) |
| Vaccinated* | 122 (60) | 955 (37) | 2663 (26) |
| Race | |||
| White | 14 (6·9) | 464 (18) | 1919 (19) |
| Black | 8 (3·9) | 123 (4·7) | 451 (4·5) |
| Asian | 1 (0·49) | 16 (0·61) | 135 (1·3) |
| Other | 0 | 2 (<0·10) | 7 (<0·10) |
| Unknown/missing | 181 (89) | 2009 (77) | 7605 (75) |
| 2009 H1N1 | n = 65 | n = 1319 | n = 6882 |
| Age–Mean (SD) | 57 ± 11 | 46 ± 15 | 47 ± 13 |
| Age–Median | 57 | 48 | 49 |
| BMI–Mean (SD) | 30 ± 6·9 | 29 ± 6·3 | 28 ± 5·9 |
| BMI–Median | 30 | 27 | 27 |
| No. (%) | No. (%) | No. (%) | |
| Normal weight | 13 (20) | 418 (32) | 2310 (34) |
| Overweight | 20 (31) | 461 (35) | 2471 (36) |
| Obese | 32 (49) | 440 (33) | 2101 (31) |
| Female | 32 (49) | 885 (67) | 4012 (58) |
| Charlson score | |||
| 0 | 27 (42) | 913 (69) | 5441 (79) |
| 1 | 12 (18) | 262 (20) | 912 (13) |
| ≥2 | 26 (40) | 144 (11) | 529 (7·8) |
| Vaccinated* | 11 (16·9) | 109 (8·3) | 379 (5·5) |
| Race | |||
| White | 32 (49) | 634 (48) | 3327 (48) |
| Black | 11 (17) | 155 (12) | 749 (11) |
| Asian | 0 | 38 (2·9) | 232 (3·4) |
| Other | 0 | 3 (0·23) | 16 (0·23) |
| Unknown/missing | 22 (34) | 489 (37) | 2558 (37) |
BMI, body mass index; SD, standard deviation; EHR, electronic health record.
Severe ILI includes only those hospitalized with ILI. This table contains data for all three influenza seasons.
*
Vaccine data were only available for those who received influenza vaccine at an HVMA site (seasonal influenza vaccine transaction recorded in electronic health record). “Other” race contains American Indian/Alaskan Natives, Native Hawaiian, or Other Pacific Islander, and those with more than one race reported.