Proof that vaccinating children aged 6 to 24 months against influenza in the hope of reducing disease spread is inconclusive. These conclusions are based on a small number of studies based on a large dataset of reasonable quality.
Most immunisation campaigns in the USA & Canada target people aged 65 years or older. There is little evidence that complications (such as ear infections and pneumonia), school absences, parental loss of workdays and over-prescribing of antibiotics, decrease after children have been vaccinated.
Tom Jefferson (Cochrane Vaccines Field, Italy) and colleagues identified and assessed 25 comparative studies that evaluated the efficacy and effectiveness of influenza vaccines in healthy children under age 16, vaccines of live viruses with weakened infectivity had 79% efficacy and 38% effectiveness in children older than two years compared with placebo or no immunisation. Inactivated vaccines had a lower efficacy (65%) than live weakened vaccines, and in children aged two years or younger they had similar effects to placebo. Effectiveness of inactivated vaccines was about 28% in children older than two years.
Although vaccines were effective in reducing long school absences they had little effect on hospital stays and respiratory disease, when compared with placebo or no intervention.
A striking difference was noted between the efficacy and effectiveness of vaccines because of the large proportion of influenza-like illness.