FluBlok Quadrivalent comparable to IIV4 in young adults

A comparison of recombinant and inactivated quadrivalent influenza vaccines found that the two vaccines demonstrated similar immunogenicity, safety and tolerability among patients aged 18 to 49 years.

 “Our study, conducted during the 2014-2015 season, was the first designed to compare two quadrivalent vaccines directly,” Lisa M. Dunkle, MD, chief medical officer at Protein Sciences, and colleagues wrote. “The primary objective was to demonstrate noninferior immunogenicity of all four vaccine antigens of RIV4 versus a licensed, inactivated quadrivalent influenza vaccine in subjects 18 to 49 years of age, the age group in which clinical efficacy of RIV3 had already been demonstrated.”

Dunkle and colleagues previously reported that in a concurrent study, the Flublok Quadrivalent (RIV4, Protein Sciences Corporation) vaccine was 30% more effective than Fluarix Quadrivalent (IIV4, GlaxoSmithKline) in patients aged 50 years or older.

The researchers conducted an observer-blind, randomized, active-controlled phase 3 trial at 10 sites in the United States, randomly assigning 1,350 patients to receive either a single dose of RIV4 or IIV4 at a 3:1 ratio. The main outcomes were post-vaccination geometric mean titer ratios for each antigen and hemagglutination inhibition seroconversion rates.

RIV4 showed a comparable immunogenicity to IIV4, Dunkle and colleagues reported. Three patients — one in the RIV4 group and two in the IIV4 group — received the wrong vaccine, and were not included in the final analysis. Both groups showed similar immunogenicity for three antigens but showed low antibody responses to the fourth antigen (influenza B/60/2008), which the researchers wrote made comparisons between the groups uninterpretable. Both groups demonstrated only mild, transient injection site reactions.

Although 10.3% of patients in the RIV4 group and 10.5% of those in the IIV4 group experienced adverse events, none of these were considered related to the study vaccine.

Dunkle and colleagues wrote that the study was limited by “the unexpectedly low antibody responses to influenza B/Brisbane.”

“However, in the concurrent clinical trial in adults 50 years of age [or older], similar protection by RIV4 and IIV4 against the circulating influenza B strains was observed, suggesting adequate immunogenicity, despite the titers, as measured,” the researchers wrote. “Overall, this trial demonstrated an acceptable degree of immunogenicity and a satisfactory safety profile of RIV4 in adults 18 to 49 years of age.” – by Andy Polhamus

Disclosures: Dunkle is an employee and shareholder of Protein Sciences Corporation, which manufactures Flublok and Flublok Quadrivalent. Please see the study for all other authors’ relevant financial disclosures.