Table 2. Incidence per 1,000 person-years of mild and severe influenza-associated acute respiratory illness in children enrolled in a pediatric respiratory infection cohort in Thailandγ.
| Healthy | High-risk | All | ||||
|---|---|---|---|---|---|---|
| Influenza cases | Adjusted incidence (95% confidence interval) | Influenza cases | Adjusted incidence (95% confidence interval) | Influenza cases | Adjusted incidence (95% confidence interval) | |
| A. Incidence by age | ||||||
| Mild or severe | ||||||
| 0–11 months | 13 | 32 (18–59) | 5 | 23 (12–42) | 18 | 28 (16–49) |
| 12–23 months | 43 | 51 (36–71) | 21 | 35 (24–52) | 64 | 44 (32–61) |
| 24–35 months | 38 | 49 (34–70) | 14 | 34 (22–51) | 52 | 42 (30–59) |
| 36–47 months | 18 | 57 (36–91) | 6 | 40 (24–66) | 24 | 51 (32–79) |
| 48–59 months | 4 | 45 (17–123) | 2 | 31 (11–87) | 6 | 40 (15–107) |
| Mild | ||||||
| 0–11 months | 12 | 31 (17–57) | 5 | 19 (10–36) | 17 | 25 (14–46) |
| 12–23 months | 40 | 47 (33–67) | 17 | 28 (18–43) | 57 | 39 (28–55) |
| 24–35 months | 35 | 44 (30–64) | 11 | 27 (17–41) | 46 | 36 (25–52) |
| 36–47 months | 16 | 52 (32–84) | 5 | 31 (18–54) | 21 | 44 (27–70) |
| 48–59 months | 4 | 45 (16–122) | 1 | 27 (10–76) | 5 | 38 (14–102) |
| Severe | ||||||
| 0–11 months | 1 | 1 (<1–12) | 0 | 3 (<1–27) | 1 | 2 (<1–17) |
| 12–23 months | 3 | 3 (1–11) | 4 | 7 (2–22) | 7 | 5 (2–13) |
| 24–35 months | 3 | 3 (1–13) | 3 | 9 (3–27) | 6 | 6 (2–16) |
| 36–47 months | 2 | 4 (1–20) | 1 | 10 (2–44) | 3 | 6 (1–26) |
| 48–59 months | 0 | 0 | 1 | 0 | 1 | 0 |
| B. Incidence by season | ||||||
| Mild or severe | ||||||
| 2012 | 40 | 44 (30–63) | 18 | 30 (19–46) | 58 | 38 (27–54) |
| 2013 | 50 | 67 (50–91) | 29 | 46 (32–66) | 79 | 58 (44–76) |
| 2014 | 15 | 39 (22–68) | 1 | 26 (14–48) | 16 | 34 (19–59) |
| Mild | ||||||
| 2012 | 35 | 39 (27–58) | 15 | 23 (15–37) | 50 | 33 (23–47) |
| 2013 | 49 | 62 (45–85) | 23 | 37 (25–55) | 72 | 51 (38–69) |
| 2014 | 14 | 40 (23–71) | 1 | 24 (13–44) | 15 | 33 (19–58) |
| Severe | ||||||
| 2012 | 5 | * | 3 | * | 8 | * |
| 2013 | 1 | * | 6 | * | 7 | * |
| 2014 | 1 | * | 0 | * | 1 | * |
Incidence was adjusted for influenza vaccination status, recent history of ARI in the household, and influenza season in (A) and for age at acute respiratory illness, influenza vaccination status, and recent history of ARI in the household in (B).
γMild, cases treated in outpatient department; severe, cases treated in inpatient department
*model not converged