Flu: effect of vaccine in elderly care home residents: a randomized trial

J Am Geriatr Soc. 2007 Dec;55(12):1912-20. doi: 10.1111/j.1532-5415.2007.01471.x.


Objectives: To determine whether assessing seroprotection after influenza vaccine and administering booster vaccination where not achieved reduces hospitalization and death. To estimate the overall seroprotection rate of influenza vaccine.

Design: A two-arm, partially blind, randomized, multicenter, parallel-group, controlled trial.

Setting: Twenty-six care homes in three South London boroughs in fall 2004.

Participants: Two hundred seventy-seven elderly permanent care home residents meeting eligibility criteria.

Intervention: Postvaccination blood samples were randomized to booster evaluation or no booster evaluation (control). If evaluation revealed inadequate seroprotection, a booster vaccine was administered.

Measurements: Primary outcome was hospitalization to end April 2005; secondary outcomes were death, antibiotic use, and seroprotection.

Results: Sixty percent of the controls and 41% of the booster evaluation group responded to routine vaccination. Booster vaccination where indicated increased seroprotection rates in the booster evaluation group to 66%. Treatment groups did not differ in any outcome measures in the intention-to-treat analysis (hospitalization odds ratio=1.02, 95% confidence interval=0.55-1.87). There was a tendency towards greater differences between groups in the per-protocol analysis than in the intention-to-treat analysis, particularly regarding seroprotection rates. The same effect was observed in the a priori exploratory analysis of residents not seroprotected after routine vaccination alone.

Conclusion: In a year without circulating influenza, there is no clinical benefit of administering a booster vaccine if routine trivalent vaccination fails to result in seroprotection. Hemagglutination titers rose in two strains postbooster vaccination but fell against the novel strain, Wyoming. The benefit of such a booster strategy when influenza is prevalent thus remains uncertain.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Chi-Square Distribution
  • Female
  • Homes for the Aged*
  • Humans
  • Immunization Programs
  • Immunization, Secondary*
  • Influenza Vaccines / administration & dosage*
  • Influenza, Human / mortality
  • Influenza, Human / prevention & control*
  • London / epidemiology
  • Male
  • Prospective Studies
  • Treatment Outcome


  • Influenza Vaccines