Title: Efficacy of Recombinant Influenza Vaccine in Adults 50 Years of Age or Older

Dunkle, LM et al.


What You Need to Know:

In adults 50 years and older with confirmed influenza-like illness, a quadrivalent, recombinant influenza vaccine (RIV4) offered better protection than a standard-dose, quadrivalent, inactivated influenza vaccine (IIV4).

Trial Design:

  • Double-blind, multicenter study compared the relative efficacy of RIV4 vs IIV4 “against reverse-transcriptase polymerase-chain-reaction (RT-PCR)–confirmed, protocol-defined, influenza-like illness caused by any influenza strain starting 14 days or more after vaccination”
  • Efficacy was assessed “during the A/H3N2-predominant 2014-2015 influenza season, when antigenic mismatch between circulating and vaccine influenza strains resulted in the reduced effectiveness of many licensed vaccines”
  • 9003 patients were randomized to receive RIV4 (containing 45μg recombinant hemagglutinin (HA)/strain + 180 g protein/dose) or IIVA4 (containing 15μg HA/strain and 60μg protein/dose)
  • Primary endpoint: “RT-PCR–confirmed, protocol defined, influenza-like illness between 14 days or more after vaccination and the end of the influenza season”
  • Modified intention-to-treat population: 8855 patients; received vaccine and completed efficacy follow-up
  • Modified per-protocol population: 8604 patients; completed per-protocol follow-up

Key Outcomes:

  • RIV4 patients: influenza attack rate of 2.2% in both the modified per-protocol population as well as the modified intention-to-treat population
  • IIV4 patients: influenza attack rate of 3.2% in the modified per-protocol population and 3.1% in the modified intention-to-treat population
  • Detected cases: influenza A/H3N2 (n=181), influenza B (n=47), nonsubtypeable influenza A (n=6)
  • “The probability of influenza-like illness was 30% lower with RIV4 than with IIV (95% confidence interval, 10 to 47; P=0.006) and satisfied prespecified criteria for the primary noninferiority analysis and an exploratory superiority analysis of RIV4 over IIV4”
  • No significant differences between the safety profiles of RIV4 and IIV4 were observed