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Flublok Quadrivalent provides better protection than IIV4
Flublok Quadrivalent was 30% more effective in preventing influenza than an egg-derived inactivated quadrivalent influenza vaccine, according to results of a randomized trial published in The New England Journal of Medicine.
Lisa M. Dunkle, MD, chief medical officer at Protein Sciences, and colleagues conducted the phase 3 to 4 trial during the 2014–2015 influenza season, which was recognized as having a low estimated vaccine effectiveness chiefly because the majority of circulating influenza A (H3N2) viruses — the most prevalent subtype — did not match the vaccine’s H3N2 component.
The trial compared the relative vaccine efficacy of Flublok Quadrivalent (RIV4, Protein Sciences) — a quadrivalent recombinant influenza vaccine approved last year by the FDA — with Fluarix Quadrivalent (IIV4, GlaxoSmithKline) among around 9,000 patients aged 50 years and older.
According to Dunkle and colleagues, there are several potential benefits of recombinant vaccines. Whereas inactivated influenza vaccines (IIVs) are made using viruses grown in eggs, leading to gene mutations, recombinant vaccines are produced using a serum-free medium, yielding hemagglutinin (HA) proteins that are genetically identical to selected influenza strains without extraneous egg proteins, formaldehyde, antibiotics or preservatives, they explained. Further, recombinant vaccines can be produced within 6 to 8 weeks compared with 6 months for egg-based vaccines, Dunkle and colleagues said.
“Reducing the burden of influenza disease requires improved vaccines, and a recombinant influenza vaccine may contribute to this public health goal,” they wrote.
From Oct. 22, 2014, to May 22, 2015, Dunkle and colleagues randomized 9,003 participants aged 50 years or older in 40 outpatient settings across the U.S. to receive either RIV4 (45 µg of recombinant HA per strain, 180 µg of protein per dose) or standard-dose IIV4 (15 µg of HA per strain, 60 µg pf protein per dose) in a double-blind trial. They compared the relative vaccine efficacy against RT-PCR–confirmed influenza-like illness caused by any strain of the virus starting 14 days or more after vaccination.
According to the results, among 8,604 patients in the modified per-protocol population, the influenza attack rate was 2.2% in patients who received RIV4 (n = 4,303) compared with 3.2% in patients who received IIV4 (n = 4,301). Among 8,855 patients in the modified intention-to-treat population, the influenza attack rate was also 2.2% in patients who received RIV4 (n = 4,427) compared with 3.1% among patients in the IIV4 arm (n = 4,428).
Dunkle and colleagues detected 234 cases of influenza during the study, including 181 cases of influenza A(H3N2). They calculated that the probability of influenza-like illness was 30% lower with RIV4 than with IIV4 (95% CI, 10 to 47) and noted that the safety profiles of the vaccines were similar.
“In conclusion,” they wrote, “this trial showed that RIV4, as compared with IIV4, improved protection against laboratory-confirmed influenza-like illness in adults 50 years of age or older. These results occurred during an influenza season characterized by widespread circulation of antigenically mismatched strains of influenza A(H3N2).” – by Gerard Gallagher
Disclosure: Please see the full study for a list of all authors’ relevant financial disclosures.