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Indirect protection from vaccinating children against influenza in households.

Tim K TsangVicky J FangDennis K M IpRanawaka A P M PereraHau Chi SoGabriel M LeungJ S Malik PeirisBenjamin John CowlingSimon Cauchemez
Published in: Nature communications (2019)
Vaccination is an important intervention to prevent influenza virus infection, but indirect protection of household members of vaccinees is not fully known. Here, we analyze a cluster household randomized controlled trial, with one child in each household randomized to receive influenza vaccine or placebo, for an influenza B epidemic in Hong Kong. We apply statistical models to estimate household transmission dynamics and quantify the direct and indirect protection of vaccination. Direct vaccine efficacy was 71%. The infection probability of unvaccinated household members in vaccinated households was only 5% lower than in control households, because only 10% of infections are attributed to household transmission. Even when that proportion rises to 30% and all children are vaccinated, we predict that the infection probability for unvaccinated household members would only be reduced by 20%. This suggests that benefits of individual vaccination remain important even when other household members are vaccinated.
Keyphrases
  • randomized controlled trial
  • double blind
  • systematic review
  • open label
  • placebo controlled