Table of contents
- Trial overview
- Phase 3 study of vaccination route
- Phase 2 comparison study in adults
- Outcomes and endpoints
- Who the studies include
- What the results mean
Trial overview
The clinical trials in this set are studying YELLOW FEVER VIRUS STRAIN 17D-204 (LIVE, ATTENUATED) through yellow fever vaccination research.[1][1] Both studies are interventional studies, which means researchers give a vaccine and then measure what happens after vaccination.[1][1]
All listed trials are authorised and focus on immune response after vaccination, not on treating active yellow fever disease.[1][1]
Phase 3 study of vaccination route
One Phase 3 trial compares three vaccination routes: intradermal, subcutaneous, and intramuscular.[1] The study uses STAMARIL and includes 222 participants.[1]
This trial asks whether the way the vaccine is given changes the immune response in the skin.[1] The brief summary says the study compares the number and proportion of skin-resident memory T cells against yellow fever virus at day 28 after vaccination.[1]
The trial includes three vaccine routes: 0.5 ml intramuscular injection, 0.1 ml intradermal use, and 0.5 ml subcutaneous injection.[1] These details matter because the study is trying to see whether route affects the immune result.[1]
Phase 2 comparison study in adults
Another trial is a Phase 2 study in adults in Europe and Asia, with an enrollment of 690 participants.[1] It compares an investigational yellow fever vaccine, called vYF, with the control vaccine STAMARIL.[1]
The main goal is to show non-inferiority, which means the investigational vaccine should not perform worse than the control vaccine by more than an allowed amount.[1] The study looks at the antibody response 28 days after one dose given on Day 01.[1]
The primary outcome is the percentage of participants in an EU group who have seroconversion in a yellow fever virus-naïve population.[1] In this trial, seroconversion is defined as a 4-fold rise in neutralizing antibody levels compared with the level before vaccination.[1]
Outcomes and endpoints
These studies mainly measure immune markers, not symptoms or disease cure.[1][1] In the Phase 3 study, the primary outcomes are the percentage and the absolute number of YFV-specific T cells within the skin-resident lymphocyte parent population at day 28, measured by flow cytometry.[1]
In the Phase 2 study, the primary outcome is the seroconversion rate in yellow fever virus-naïve participants after vaccination.[1] This endpoint is used to judge how strongly the body responds to the vaccine.[1]
Who the studies include
The available data show that both trials are focused on adults.[1] One study includes adults in Europe and Asia, while the other compares vaccine routes in a larger group of 222 participants.[1][1]
The Phase 2 study specifically mentions a yellow fever virus-naïve population, which means participants who have not previously had a yellow fever virus immune response before the study.[1] This helps researchers measure the response to the study vaccine more clearly.[1]
What the results mean
These trials are designed to help researchers understand whether different vaccination routes or different vaccine products lead to a strong immune response.[1][1] The Phase 3 study looks at immune cells in the skin, while the Phase 2 study looks at antibody response in blood.[1][1]
Because the studies are authorised and still focused on immune outcomes, they are part of the research process that helps compare vaccination strategies for yellow fever prevention.[1][1]
