Challenge of conducting a placebo-controlled randomized efficacy study for influenza vaccine in a season with low attack rate and a mismatched vaccine B strain: a concrete example
2009

Influenza Vaccine Efficacy Study

Sample size: 6203 publication Evidence: low

Author Information

Author(s): Jiří Beran, Veronika Wertzova, Karel Honegr, Eva Kaliskova, Martina Havlickova, Jiří Havlik, Helena Jirincova, Pascale Van Belle, Varsha Jain, Bruce Innis, Jeanne-Marie Devaster

Primary Institution: The Vaccination and Travel Medicine Center, Hradec Kralove, Czech Republic

Hypothesis

What is the efficacy of a trivalent inactivated split virus influenza vaccine (TIV) against culture-confirmed influenza A and/or B in adults during the 2005/2006 season?

Conclusion

The study was unable to demonstrate the efficacy of TIV due to a low attack rate and a mismatch between the circulating B strain and the vaccine strain.

Supporting Evidence

  • The attack rate in the vaccine group was 0.7%, and in the placebo group, it was 0.9%.
  • Only 46 culture-confirmed cases were found in the study cohort.
  • 35 of the 36 influenza B isolates were identified as antigenically unrelated to the vaccine B strain.

Takeaway

The study tried to see if a flu vaccine worked, but there weren't enough flu cases to tell if it was effective.

Methodology

Randomized, double-blind, placebo-controlled study with 6203 subjects receiving either TIV or placebo.

Limitations

The study faced a low attack rate and a mismatch between the vaccine strain and circulating strains.

Participant Demographics

Healthy adults aged 18 to 64 years, predominantly white Caucasian.

Statistical Information

Confidence Interval

95% CI -49.1% to 58.5%

Digital Object Identifier (DOI)

10.1186/1471-2334-9-2

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