Table 2.
Incidence Rates of Acute Upper Respiratory Tract Infection Among 115 Participants Aged 6–15 Years Who Received Trivalent Inactivated Influenza Vaccine or Placebo
| TIV (n = 69) |
Placebo (n = 46) |
||||||
|---|---|---|---|---|---|---|---|
| Variable | Ratea | (95% CI) | Ratea | (95% CI) | Relative Risk (95% CI) | P Value | |
| Winter 2009 | |||||||
| ARIb episodes | 2080 | (1530–2830) | 2260 | (1550–3300) | 0.92 | (.57–1.50) | .74 |
| FARIb episodes | 609 | (346–1070) | 753 | (392–1450) | 0.81 | (.34–1.92) | .63 |
| Summer 2009 | |||||||
| ARIb episodes | 1510 | (1130–2020) | 1160 | (757–1780) | 1.30 | (.78–2.18) | .31 |
| FARIb episodes | 658 | (424–1020) | 442 | (221–884) | 1.49 | (.65–3.38) | .33 |
Abbreviations: ARI, acute respiratory illness; CI, confidence interval; FARI , febrile acute respiratory illness; TIV, trivalent inactivated influenza vaccine.
a Incidence rates were estimated as the number of ARI or FARI episodes per 1000 person-years of follow-up.
b ARI was defined as at least 2 of the following symptoms: body temperature ≥37.8°C, cough, sore throat, headache, runny nose, phlegm, and myalgia; FARI was defined as body temperature ≥37.8°C plus cough or sore throat.