The characteristics of all click here vaccines have been previously reported [10], [11] and [12]. Both studies were conducted in accordance with the Code of Ethics of the World Medical Association

(Declaration of Helsinki). Parents or guardians recorded daily temperatures and signs or symptoms of respiratory illness and were instructed to promptly notify study personnel if their child developed qualifying symptoms. They were also contacted every 7–10 days throughout the influenza season. Nasal swabs were collected if a child had ≥1 of the following: acute otitis media (suspected or diagnosed), fever, pneumonia, pulmonary congestion, shortness of breath, or wheezing, or ≥2 of the following symptoms concurrently: chills, cough, decreased activity, headache, irritability, muscle aches, pharyngitis, rhinorrhea, or vomiting. Central laboratories evaluated nasal swabs for the presence of influenza virus by viral culture; wild-type serotypes were identified using antigenic methods. Laboratory-confirmed cases of influenza were classified as moderate/severe influenza if there was any documentation

of fever >39 °C, acute otitis media, or lower respiratory tract illness (defined as healthcare provider-confirmed shortness of breath, pulmonary congestion, pneumonia, bronchiolitis, bronchitis, wheezing, or croup). All other cases were classified as milder influenza. All children ≥24 months of age were retained in this post hoc analysis. ABT-263 mw Efficacy was calculated as one minus the relative risk of laboratory-confirmed influenza regardless of antigenic match with LAIV versus placebo or IIV. Efficacy was evaluated first against moderate/severe cases of influenza in all children, then against mild cases of influenza only. The 95% CIs of the vaccine efficacy point estimates were obtained by a log-binomial regression. Results

from the two studies were not combined because study 1 assessed LAIV efficacy versus placebo, whereas study 2 assessed LAIV efficacy versus IIV. A total of 1330 children ≥24 months of age in year 1 (LAIV, n = 897; placebo, n = 433) and 1358 children in year 2 (LAIV, n = 917; placebo, n = 441) were enrolled in study 1. The attack rates of moderate/severe influenza already were 0.6% (5/897) in year 1 and 1.1% (10/917) in year 2 in the LAIV group versus 12.0% (52/433) in year 1 and 9.5% (42/441) in year 2 in the placebo group, resulting in efficacy estimates of 95.4% (95% CI: 88.5, 98.1) in year 1 and 88.5% (77.4, 94.9) in year 2 ( Figs. 1A and 1B). The attack rates of mild influenza were 0.6% (5/892) in year 1 and 0.6% (5/907) in year 2 in the LAIV group versus 6.6% (25/381) in year 1 and 3.6% (14/399) in year 2 in the placebo group, resulting in efficacy estimates of 91.4% (77.9, 96.7) and 84.2% (56.7, 94.3) in year 1 and year 2, respectively ( Figs. 1A and 1B). In year 1, both A/H3N2 and B strains circulated. Efficacy against moderate/severe influenza for A/H3N2 and B strains was 95.7% (86.5, 99.2) and 95.8% (83.0, 99.