Flublok Quadrivalent

Efficacy against Laboratory-Confirmed Influenza

Study 3

• The efficacy of Flublok (trivalent formulation) is relevant to Flublok Quadrivalent.

• The efficacy of Flublok (trivalent formulation) was based on a randomized, observer-blind, placebo-controlled trial which included 4648 participants 18 to 49 years of age. Participants were randomly assigned 1:1 to receive a single dose of Flublok (trivalent formulation) or placebo.

• The primary efficacy endpoint of Study 3 was Centers for Disease Control-defined influenza-like illness (CDC-ILI) with a positive culture for an influenza virus strain antigenically resembling a strain represented in Flublok. CDC-ILI is defined as fever of ≥100°F oral accompanied by cough, sore throat, or both on the same day or on consecutive days. Attack rates and vaccine efficacy (VE), defined as the reduction in the influenza rate for Flublok relative to placebo, were calculated for the total vaccinated cohort (n=4648).  

• The vaccine efficacy for Flublok (trivalent formulation) was 44.8% against all strains, regardless of antigenic match, isolated from any subject with an ILI, not necessarily meeting the CDC-ILI criteria.

Study 2

• The efficacy of Flublok Quadrivalent was based on a randomized, observer-blind, active-controlled trial which included 8963 participants 50 years of age and older. Participants were randomly assigned 1:1 to receive a single dose of Flublok Quadrivalent or a US-licensed quadrivalent inactivated influenza vaccine (Comparator, Fluarix Quadrivalent).

• Real-time polymerase chain reaction (rtPCR)–confirmed influenza was assessed by active and passive surveillance for influenza-like illness (ILI) beginning 2 weeks post-vaccination until the end of the influenza season, approximately 6 months post- vaccination. The primary efficacy endpoint of Study 2 was rtPCR-positive, protocol-defined ILI due to any strain of influenza.

• The relative vaccine efficacy of Flublok Quadrivalent vs comparator against laboratory-confirmed influenza, regardless of antigenic similarity to vaccine antigens were as followed:

• All rtPCR-positive influenza: 30% (95% CI, 10-47)

• All rtPCR-positive influenza A: 36% (95% CI, 14-53)

• All rtPCR-positive influenza B: 4% (95% CI, -72, 46)

• All culture-confirmed protocol-defined ILI: 43% (95% CI, 21-59)

Immunogenicity of Flublok Quadrivalent

Study 1

• The randomized, observer-blind, active-controlled, multicenter trial evaluated the immunogenicity of Flublok Quadrivalent compared with a US-licensed quadrivalent inactivated influenza vaccine (Fluarix Quadrivalent) in 1350 patients 18 to 49 years of age. Patients were randomly assigned 3:1 to receive Flublok Quadrivalent or comparator.

• Post-vaccination immunogenicity was evaluated on sera obtained 28 days after administration of a single dose of study vaccine. Hemagglutination inhibition (HI) geometric mean titers (GMTs) were determined for the two vaccine groups for each vaccine antigen. Immunogenicity was compared by calculating the difference in seroconversion rates (SCR) and the ratios of GMTs of Comparator to Flublok Quadrivalent.

• Flublok Quadrivalent met the success criterion for GMTs for 3 of the 4 antigens but not for the B/Victoria lineage antigen. Flublok Quadrivalent met the success criterion for SCRs for 3 of the 4 antigens but not for the B/Victoria lineage antigen