TICK-BORNE ENCEPHALITIS VIRUS, STRAIN K23, ADSORBED ON HYDROGENATED ALUMINUM HYDROXIDE, INACTIVATED

What is Tick-Borne encephalitis virus?

Tick-Borne Encephalitis Virus (TBEV), strain K23, adsorbed on hydrogenated aluminum hydroxide and inactivated, is a virus-based active substance used in vaccines against tick-borne encephalitis.

How does Tick-Borne encephalitis virus work?

The inactivated virus in the vaccine is designed to teach the immune system to recognise TBEV without causing infection. When injected into the muscle, it prompts the body to produce antibodies (IgM and IgG) and T-cells that can respond to the virus if a person is later bitten by an infected tick.^[1] The clinical trial is specifically measuring both the T-cell response (using a novel rapid release assay) and the antibody response (using commercially available IgM and IgG assays) to understand how well and how long protection lasts.^[1]

Which conditions is it used or studied for?

• Tick-borne encephalitis — a viral infection of the brain and central nervous system transmitted by tick bites. The vaccine is authorised to help prevent this disease, and the current trial is studying immune responses in people who have had TBE or have been vaccinated against it.^[1]

How is Tick-Borne encephalitis virus given?

The vaccine is given as an intramuscular injection. The product is a 0.5 ml suspension for injection supplied in a pre-filled syringe.^[1] In the authorised trial, participants receive either FSME-IMMUN Vuxen (Pfizer) or Encepur (Bavarian Nordic), both of which are inactivated TBE vaccines.^[1]

What do the clinical trials show?

One Phase 3 interventional trial (2023-509575-16-00) is authorised to investigate immune responses to TBE vaccination and infection.^[1] The trial plans to enroll 100 participants across four cohorts: people hospitalised for TBE within the last 6 months, people previously hospitalised for TBE at least 6 months ago, healthy or immunosuppressed people starting TBE vaccination, and healthy or immunosuppressed people who have received TBE vaccination in the past.^[1] The primary outcome is the concentration of cytokines detected by a novel rapid release T-cell assay, compared with antibody levels measured by commercially available IgM and IgG assays.^[1] The trial aims to evaluate the magnitude and durability of T-cell responses in relation to antibody levels, time since infection or vaccination, number of vaccine doses, and vaccine manufacturer.^[1]

What side effects are known?

No side effect data specific to this substance is available in the provided sources. The NHS formulary source notes that TBE vaccine is not commissioned for travel vaccination in the Humber and North Yorkshire region, but does not describe side effects.^[2]