FDA Approves First Monkeypox, Smallpox Vaccine

The US Food and Drug Administration (FDA) has approved the first live, non-replicating vaccine indicated for the prevention of smallpox and monkeypox.

The Jynneos Smallpox and Monkeypox Vaccine, Live, Non-Replicating, from Bavarian Nordic A/S, was approved for preventing smallpox and monkeypox in adults aged 18 years or older who have been determined to be at high risk for either infection.

With the indication, it also becomes the only FDA-approved vaccine for the prevention of monkeypox—a rare virus infection with similar, mild symptoms to smallpox. The possibly fatal disease last made headlines in the US during a 2003 outbreak, when the first human case was reported outside of Africa.

The vaccine will be made available for clinically determined high-risk patients, and will also be included in the Strategic National Stockpile, the US’ greatest surplus of pharmaceuticals and medical supplies for us in potentially severe public health emergencies.

The Jynneos vaccine does not contain strains of neither the smallpox nor monkeypox virus, but is rather made from the vaccinia virus, which resembles a less harmful form of the variola or monkeypox virsuses. The vaccine contains a modified form of the virus which does not cause disease in humans and is non-replicating.

The efficacy of the vaccine in preventing smallpox was evidenced in a clinical trial comparing immune responses in treated patients to that of ACAM2000, a vaccine approved for smallpox prevention. A group of 400 healthy adults aged 18-42 years old without prior smallpox vaccination were split 1:1 to either 2 doses of Jynneos split by 28 days, or 1 dose of ACAM2000.

Patients vaccinated with Jynneos reported a non-inferior immune response to that of the ACAM2000-vaccinated group.

The vaccine’s efficacy in preventing monkeypox was evidenced by the antibody responses observed in the same smallpox clinical trial participants, as well as from primate trials showing protection from the virus in animals exposed to it.

Jynneos’ safety was reported through data from 7800-plus individuals who received at least 1 dose of the vaccine. Commonly reported side effects included pain, redness, swelling, itching, firmness at the injection site, muscle pain, headache, and fatigue.

Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, noted a large portion of the US and global population has no immunity from smallpox due the disease’s eradication decades ago—which led to the end of routine vaccination.

“Therefore, although naturally occurring smallpox disease is no longer a global threat, the intentional release of this highly contagious virus could have a devastating effect,” Marks said in a statement. “Today's approval reflects the US government's commitment to preparedness through support for the development of safe and effective vaccines, therapeutics, and other medical countermeasures."