In short
INFLUENZA A VIRUS, SUBTYPE H3N2, STRAIN A/DISTRICT OF COLUMBIA/27/2023-LIKE VIRUS A/VICTORIA/800/2024 CVR-289, LIVE is one component of a seasonal influenza vaccine authorised in the EU as Flucelvax. It is an inactivated surface antigen vaccine prepared in cell cultures. One completed Phase 3 trial with 30 participants examined how intramuscular influenza vaccination affects memory immune responses in the nasal mucosa.
Key points
- Authorised medicine: Marketed as Flucelvax in the EU, supplied by Seqirus Netherlands B.V.
- Vaccine type: Inactivated influenza vaccine (surface antigen) prepared in cell cultures, given by intramuscular injection.
- Studied condition: Adults seeking active immunisation against seasonal influenza virus.
- Trial status: One completed Phase 3 trial with 30 participants.
- Main measurement: Frequency of resident memory lymphocytes in nasal mucosa before and after vaccination.
What is influenza A (H3N2) vaccine?
INFLUENZA A VIRUS, SUBTYPE H3N2, STRAIN A/DISTRICT OF COLUMBIA/27/2023-LIKE VIRUS A/VICTORIA/800/2024 CVR-289, LIVE is a strain of influenza A virus used as an antigen in seasonal influenza vaccines. In the EU clinical trial registry, it appears as part of the product Flucelvax, an influenza vaccine that contains surface antigens that are inactivated and prepared in cell cultures. The vaccine is authorised as a medicine in the EU under authorisation number EU/1/24/1879/001, supplied by Seqirus Netherlands B.V. The World Health Organization (WHO) has published information on cell culture-derived candidate vaccine viruses for the A(H3N2) lineage, noting that these are developed and analysed by WHO Collaborating Centres for use in vaccine production.
How does influenza A (H3N2) vaccine work?
Influenza vaccines containing this H3N2 strain are designed to stimulate the immune system against the influenza virus. The strain is an inactivated surface antigen, meaning it cannot cause infection but can trigger an immune response. The WHO states that candidate vaccine viruses such as this one undergo antigenic and genetic analysis, including haemagglutination inhibition or virus neutralisation tests, to confirm they match the recommended virus strains for the influenza season. The clinical trial listed in the registry examined how vaccination affects resident memory lymphocytes in the nasal mucosa and peripheral memory lymphocytes with respiratory tropism.
Which conditions is it used or studied for?
- Seasonal influenza prevention: The vaccine is used for active immunisation of adults against seasonal influenza virus.
How is influenza A (H3N2) vaccine given?
The vaccine is provided as a suspension for injection in a pre-filled syringe and is given by intramuscular injection. In the clinical trial, the dose used was 0.5 ml.
What do the clinical trials show?
One completed Phase 3 trial (2025-521217-46-00) included 30 adult participants seeking active immunisation against seasonal influenza. The trial compared Flucelvax with two other inactivated influenza vaccines, VaxigripTetra and Influvac Tetra, all given as 0.5 ml intramuscular injections. The primary outcome measured the frequency of resident memory lymphocytes in the nasal mucosa and the expression rate of migration markers towards the respiratory mucosa on peripheral memory lymphocytes before and after vaccination.