In short
Clinical trials are studying YELLOW FEVER VIRUS, STRAIN VYF-247, LIVE in adults to compare it with an existing yellow fever vaccine. The main goal is to check immune response, especially seroconversion, in people who have not had yellow fever vaccine before. The study is authorized and is being done in Europe and Asia.
Key points
- Clinical trials of YELLOW FEVER VIRUS, STRAIN VYF-247, LIVE are studying a yellow fever vaccine in adults. The trial compares the investigational vaccine with Stamaril in Europe and Asia. It is a Phase 2, interventional study with 690 planned participants. The main focus is immune response in yellow fever vaccine-naïve adults in the EU. The key endpoint is seroconversion 28 days after vaccination, measured by neutralizing antibody levels.
Trial overview
This study is an interventional clinical trial, which means participants receive a vaccine so researchers can compare results between groups. It is studying YELLOW FEVER VIRUS, STRAIN VYF-247, LIVE against the control vaccine Stamaril in adults with yellow fever.
The trial is authorised and planned for 690 participants. Its brief summary says the main purpose is to show non-inferiority, meaning the new vaccine should work at least nearly as well as the comparison vaccine.
Who can participate
The trial includes adults in Europe and Asia. A main analysis is planned for participants in the EU who are YF-naïve, meaning they have not been vaccinated against yellow fever before.
This focus on YF-naïve people matters because the study wants to see how a first yellow fever vaccine dose works in people without prior yellow fever vaccine exposure.
What the study measures
The main endpoint is the percentage of participants who show seroconversion to yellow fever virus 28 days after vaccination. Seroconversion is defined in the study as a 4-fold increase in neutralizing antibody levels compared with the level before vaccination.
Neutralizing antibodies are immune proteins that can block a virus from infecting cells, so this measurement helps show whether the vaccine triggered a strong immune response.
Study design and phase
This is a Phase 2 trial. Phase 2 studies usually look more closely at whether a vaccine works and continue to evaluate the immune response in a larger group than early-phase studies.
The study compares one dose of YELLOW FEVER VIRUS, STRAIN VYF-247, LIVE with one dose of Stamaril, both given on Day 01 by subcutaneous use, according to the trial summary. The main comparison is the antibody response 28 days after vaccination.
Where the trial is being done
The study is described as being in Europe and Asia. The brief summary specifically highlights the EU group for the main non-inferiority analysis in YF-naïve participants.
Key terms explained
Seroconversion means the blood test shows a clear immune response after vaccination. In this trial, it means antibody levels increased four times or more compared with before the vaccine.
Non-inferiority means the study is checking whether the investigational vaccine is not worse than the comparison vaccine by an important amount. This is a common way to compare vaccines when the goal is to show similar protection.
Neutralizing antibodies are part of the body's defense system and are measured here to understand the vaccine response. A higher level after vaccination suggests the immune system has reacted to the vaccine.