Two outbreaks of influenza A (H3N2) in a Japanese nursing home in the winter of 1996-1997, with differing vaccine efficacy

Tohoku J Exp Med. 1999 Aug;188(4):289-98. doi: 10.1620/tjem.188.289.


Sixty of 128 (46.9%) residents of a nursing home were immunized with two doses of the trivalent split influenza vaccine. They developed 7.4-11.5-fold antibody increases, with a 69-82% protection rate, presenting good immune response rates to the influenza vaccine. Two outbreaks of influenza A (H3N2) occurred. There were no significant antigenic differences among the vaccine strain and the strains isolated from both outbreaks in haemagglutination-inhibition tests, suggesting that the second might have been a reoccurrence. There were no residents who were infected in both outbreaks. The vaccine efficacy against clinical illness in the first outbreak of typical influenza-like-illness (ILI) was 51% (relative risk: 0.49), and the febrile period was reduced significantly by vaccination. In the second outbreak, however, in which all patients had atypical ILI with a high fever but not respiratory symptoms, vaccine efficacy was not apparent for unknown reason.

Publication types

  • Clinical Trial

MeSH terms

  • Aged
  • Aged, 80 and over
  • Disease Outbreaks / prevention & control*
  • Female
  • Fever / epidemiology
  • Hemagglutination Inhibition Tests
  • Humans
  • Influenza A Virus, H3N2 Subtype*
  • Influenza A virus* / immunology
  • Influenza A virus* / isolation & purification
  • Influenza Vaccines / therapeutic use*
  • Influenza, Human / epidemiology*
  • Influenza, Human / prevention & control*
  • Influenza, Human / virology
  • Japan / epidemiology
  • Male
  • Prospective Studies


  • Influenza Vaccines