An Experimental Medicine Decipher of a Minimum Correlate of Cellular Immunity
Objective: To compare, after challenge with a structurally heterologous vaccine, the differences in levels of viremia between healthy adults who received primary vaccination with either YF17D vaccine, chimeric JE-YF17D vaccine, or inactivated JE vaccine. 58 subjects will be randomised into 1 of 2 arms (Arm B1 and Arm B2) in a 1:1 ratio, in a double-blind fashion. Subjects in Arm B1 will receive JE-YF17D vaccine (Imojev, Sanofi Pasteur) on Day 0 followed by YF17D vaccine (Stamaril, Sanofi Pasteur) on Day 28. Subjects in Arm B2 will receive Stamaril on Day 0 followed by Imojev on Day 28. Arm B3 will be conducted as a separate single-arm open label design in 14 subjects. Subjects in Arm B3 will receive inactivated JE vaccine (Ixiaro, Valneva) on Day 0 followed by Stamaril on Day 28. The rationale for these three study arms is as follows: Arm B1 will show the impact low levels of viremia, and the resultant low levels of virus-specific CD4+ and CD8+ T cells, would have on YF17D infection. In contrast, YF17D vaccination in Arm B2 would produce high levels of viremia, and in turn high levels virus-specific T cells, thus likely ameliorating JE-YF17D infection. Arm B3 will serve as the control arm, as vaccination with inactivated JE vaccine would not produce any YF17D-specific T cell response. Notably, the first vaccination in Arms B1 and B2 would also provide the viremia response in the absence of virus-specific T cells, which would serve as a reference point to interpret the outcome of the second vaccination.
• Healthy adults, 21-45 years of age at time of screening
• Willing to comply to study procedures and adhere to study schedule visits.
• Satisfactory baseline medical assessment as assessed by physical examination and a stable health status. The laboratory values must be within the normal range of the assessing site or show abnormalities that are deemed not clinically significant as judged by the investigator. A stable health status is defined as the absence of a health event satisfying the definition of a serious adverse event.
• Accessible vein for blood collection.
• Ability to provide informed consent.
• Female subjects of non-child bearing potential due to surgical sterilization (hysterectomy or bilateral oophorectomy or tubal ligation) or menopause. Post-menopausal subjects must have had at least 12 months of natural (spontaneous) amenorrhea
• Female subjects of child bearing potential with negative urine pregnancy tests on the day of screening and vaccination.
• Both male (if he has a partner of childbearing potential) and female subjects (of childbearing potential) must agree to use adequate and reliable contraceptive measures (e.g. spermicides, condoms, contraceptive pills) or practice abstinence for 10 days after vaccination.