INFLUENZA VIRUS A/VICTORIA/4897/2022 (H1N1)PDM09 - LIKE STRAIN (A/NORWAY/31694/2022, MEDI 369815)

Table of contents

• What is Influenza Virus A/VICTORIA/4897/2022?
• How does Influenza Virus A/VICTORIA/4897/2022 work?
• Which conditions is it used or studied for?
• How is Influenza Virus A/VICTORIA/4897/2022 given?
• What do the clinical trials show?

What is influenza virus A/VICTORIA/4897/2022?

The full name is shortened here to Influenza Virus A/VICTORIA/4897/2022.

How does influenza virus A/VICTORIA/4897/2022 work?

As a live attenuated influenza virus, the strain in the nasal spray vaccine is weakened so that it does not cause influenza illness in healthy people. When given intranasally, the weakened viruses replicate in the cooler lining of the nose and trigger an immune response directly in the respiratory tract. The clinical trials listed here investigated how this nasal immune response develops, measuring virus shedding after vaccination and the production of mucosal antibodies and immune cells in nasal fluid.^[1][2][3]

Which conditions is it used or studied for?

• Influenza — the vaccine is used to protect against seasonal influenza. Two of the three trials enrolled participants with influenza as the condition of interest, and one trial enrolled healthy individuals.^[1][3][2]

How is influenza virus A/VICTORIA/4897/2022 given?

The vaccine is given as a nasal spray suspension for intranasal use.^[1] In the trials, Fluenz nasal spray suspension was administered intranasally; one trial also used an intramuscular comparator vaccine (Vaxigrip Tetra).^[2] The product is not given by injection.

What do the clinical trials show?

Three Phase 3 interventional trials investigated this vaccine strain, all focused on how the nasal spray vaccine builds immunity in the respiratory tract. Two trials are completed and one is authorised but not yet started.^[1][2][3]

The trials measured different aspects of the nasal immune response. One completed trial with 20 children measured the presence or absence of viral shedding of vaccine strains after the first and second dose, using nasal lining fluid collected by nasosorption and analysed with RT-qPCR.^[1] Another completed trial with 55 participants measured both cellular and humoral immune responses, including antigen-activated CD4+ T-lymphocytes and the number of participants with at least a four-fold rise in mucosal antibody titres against each vaccine virus haemagglutinin antigen.^[3] The authorised trial with 60 healthy individuals will measure the fold change in influenza-specific IgA levels in nasal fluid at day 21 after intranasal vaccination compared to intramuscular vaccination.^[2]

Enrolment across the three trials ranged from 20 to 60 participants. The largest trial enrolled 60 healthy individuals, and the smallest enrolled 20 children.^[1][2]