JYNNEOS Rx

Vaccine Effectiveness

• Vaccine effectiveness against smallpox was inferred by comparing the immunogenicity of Jynneos to a licensed smallpox vaccine (ACAM2000) based on a Plaque Reduction Neutralization Test (PRNT) using the Western Reserve strain of vaccinia virus and was supported by efficacy data from animal challenge studies. 

• Vaccine effectiveness against monkeypox was inferred from the immunogenicity of Jynneos in a clinical study and from efficacy data from animal challenge studies. 

Immunogenicity – (Study 7)

• The randomized, open-label study was conducted at US military facilities in South Korea. The study compared the immunogenicity of Jynneos to ACAM2000 in healthy smallpox vaccine-naïve 433 adults 18 through 42 years of age. Patients were randomly assigned 1:1 to receive 2 doses of Jynneos (28 days apart) or 1 dose of ACAM2000.

• The primary immunogenicity endpoint was geometric mean titer (GMT) of vaccinia neutralizing antibodies assessed by PRNT at “peak visits” defined as two weeks after the second dose of JYNNEOS and four weeks after the single dose of ACAM2000.

• The GMT of vaccinia neutralizing antibodies assessed post-vaccination at “peak visits” for Jynneos was 152.8 vs 84.4 for ACAM2000.

• The PRNT GMTs at two and four weeks after the first dose of Jynneos (prior to the second dose), were 23.4 (95% CI: 20.5, 26.7) and 23.5 (95% CI: 20.6, 26.9), respectively. The PRNT GMT at two weeks after the single dose of ACAM2000 was 23.7 (95% CI: 20.9, 26.8).