Safety and efficacy of live attenuated influenza vaccine in children 2–7 years of age

Three pivotal trials supported the licensure of live attenuated influenza vaccine (LAIV) for children ≥2 years of age: 2 placebo-controlled studies each conducted over 2 seasons, and a 1-year trial comparing LAIV with trivalent inactivated influenza vaccine (TIV). Analyses were conducted to evaluate the safety and efficacy of LAIV in the subgroup of children ≥2 years of age from these trials. Efficacy was demonstrated compared with placebo in children aged 2–7 years in seasons with matched strains (69.2% [95% CI: 52.7, 80.4] and 94.6% [95% CI: 88.6, 97.5]), seasons with primarily mismatched strains (87% [95% CI: 77.0, 92.6]), and during late season epidemics (73.8% [95% CI: 40.4, 89.4]). Compared with TIV recipients, LAIV recipients aged 2–5 years had 52.5% (95% CI: 26.7, 68.7) and 54.4% (95% CI: 41.8, 64.5) fewer cases of influenza illness against matched and mismatched strains, respectively. No unusual or unexpected adverse reactions were noted. The adverse reactions most commonly associated with LAIV were runny nose/nasal congestion and low-grade fever. Hospitalizations and medically significant wheezing were increased in children 6–11 and 6–23 months of age who received LAIV, respectively, but were not increased in children 2–5 years of age.