General Information

Jynneos is an attenuated, live, non-replicating smallpox and monkeypox vaccine.

Jynneos is specifically indicated for the prevention of smallpox and monkeypox disease in adults 18 years of age and older determined to be at high risk for smallpox or monkeypox infection.

Jynneos is supplied as a suspension for subcutaneous injection. Administer two doses (0.5 mL each) of Jynneos 4 weeks apart.

Mechanism of Action

Jynneos is an attenuated, live, non-replicating smallpox and monkeypox vaccine that elicits humoral and cellular immune responses to orthopoxviruses. Vaccinia neutralizing antibody responses in humans were evaluated to establish the effectiveness of Jynneos for prevention of smallpox and monkeypox.

Side Effects

Adverse effects associated with the use of Jynneos may include, but are not limited to, the following:

• injection site reactions (pain, redness, swelling, induration, itching)
• muscle pain
• headache
• fatigue
• nausea
• myalgia
• chills

Serious adverse reactions were reported in 0.05% of subjects who received Jynneos and included Crohn’s disease, sarcoidosis, extraocular muscle paresis and throat tightness

Clinical Trial Results

The FDA approval of Jynneos for smallpox was based on a comprehensive development program, comprising a total of 7,871 subjects aged 18 through 80 years who received at least 1 dose (7,109 smallpox vaccine-naïve and 762 smallpox vaccine-experienced individuals) across 22 clinical trials. Among these trials were two Phase 3 studies, both of which showed non-inferiority in terms of immunogenicity measured by plaque reduction neutralization test of Jynneos compared to ACAM2000, a replicating smallpox vaccine currently licensed and marketed in the U.S. 

The FDA approval for monkeypox was based on survival data obtained in lethal monkeypox virus challenge studies in non-human primates. Overall survival in various models ranged from 80% to 100% of Jynneos-vaccinated animals compared to 0-40% in control animals. 

The safety of Jynneos was evaluated in smallpox vaccine-naïve healthy adults, in healthy adults previously vaccinated with a smallpox vaccine, in HIV-infected adults, and in adults with atopic dermatitis.