In short
mRNA Encoding Influenza B Virus, strain B/Austria/1359417/2021 (B/Victoria lineage), haemagglutinin, is an investigational messenger RNA (mRNA) component that encodes the haemagglutinin protein of an influenza B virus. It is being studied as part of a combination vaccine against influenza and COVID-19 in adults aged 65 years and older. The current evidence comes from one authorised Phase 3 trial planning to enrol 410,000 participants.
MRNA ENCODING INFLUENZA B VIRUS, STRAIN B/AUSTRIA/1359417/2021 (B/VICTORIA LINEAGE), HAEMAGGLUTININ is an investigational messenger RNA (mRNA) component that carries the genetic code for the haemagglutinin protein of an influenza B virus from the B/Victoria lineage. It is being studied as part of a combination vaccine product. The only registered trial for this substance is a Phase 3 study that plans to enrol 410,000 adults aged 65 years and older.
Key points
- Phase 3 trial authorised to evaluate a combination influenza/COVID-19 vaccine in adults aged 65 and older.
- The trial plans to enrol 410,000 participants, making it a very large pragmatic study.
- The main outcomes are medically attended influenza and/or COVID-19 and hospitalisation due to either infection.
- The study compares the combination vaccine with same-day co-administration of a high-dose influenza vaccine and a COVID-19 mRNA vaccine.
- The trial record is available in the EU Clinical Trials Information System under number 2026-526720-49-00.
What is mRNA Encoding influenza B virus?
mRNA Encoding Influenza B Virus, strain B/Austria/1359417/2021 (B/Victoria lineage), haemagglutinin, is an mRNA-based vaccine component. mRNA vaccines work by delivering a short piece of genetic material that instructs cells to make a specific viral protein. In this case, the protein is haemagglutinin, a surface protein of the influenza B virus that helps the virus enter cells. The substance is investigational, meaning it has not been authorised as a standalone medicine. It is used as a component of an investigational combination vaccine called mCombriax (mRNA-1083), which targets both influenza and COVID-19.
How does mRNA Encoding influenza B virus work?
The mRNA encodes the haemagglutinin protein of the influenza B virus. After injection, cells take up the mRNA and produce haemagglutinin. The immune system then recognises this protein as foreign and builds an immune response, including antibodies, against it. This is intended to prepare the body to fight off a future infection with influenza B viruses of the B/Victoria lineage. The combination product pairs this influenza component with an mRNA component targeting SARS-CoV-2, the virus that causes COVID-19.
Which conditions is it used or studied for?
This substance is studied as part of a combination vaccine for the prevention of two infections:
- Influenza infection — a respiratory illness caused by influenza viruses, including influenza B.
- SARS-CoV-2 infection — the infection that causes COVID-19.
Both conditions are studied together in the registered trial, which focuses on adults aged 65 years and older.
How is mRNA Encoding influenza B virus given?
The substance is given as part of a dispersion for injection in a pre-filled syringe, administered by intramuscular injection. In the registered trial, the combination vaccine containing this component is given as a single injection, while the comparison arm receives two separate injections on the same day: a high-dose influenza vaccine and a COVID-19 mRNA vaccine.
What do the clinical trials show?
Only one trial is registered for this substance. It is a Phase 3, pragmatic, randomised trial with a planned enrolment of 410,000 participants. The trial has been authorised but its results are not yet available. The study compares the combination vaccine mCombriax (mRNA-1083) with same-day co-administration of the active comparators: high-dose influenza vaccine (Efluelda) and a COVID-19 mRNA vaccine (Spikevax JN.1).
What are the trials measuring?
The primary endpoints are the occurrence of medically attended influenza and/or COVID-19, and hospitalisation due to influenza and/or COVID-19. In other words, the study measures whether the combination vaccine is as effective as the two separate vaccines in preventing illness that leads to a medical visit or a hospital stay.
Who can take part in these trials?
The trial enrols adults aged 65 years and older. This age group is chosen because older adults are at higher risk of severe illness from both influenza and COVID-19. The study is described as pragmatic, meaning it is designed to reflect real-world conditions as closely as possible.