FDA Approves Freeze-Dried Formulation of Smallpox, Mpox Vaccine
The approval expands the flexibility of storing the vaccine to protect against smallpox events or mpox outbreaks.
The FDA approved a freeze-dried formulation of a smallpox and mpox vaccine, live, nonreplicating (Jynneos), for the prevention of smallpox and mpox, formerly known as monkeypox, in adults 18 years and older. The approval expands the flexibility of storing the vaccine to protect against smallpox events or mpox outbreaks.1
The new formulations improve transportation, storage conditions, and shelf life for long-term stockpiling. | Image Credit: MargJohnsonVA | stock.adobe.com
“Today’s FDA approval represents a significant milestone in our development of this next generation of Jynneos and in our collaborative efforts with the US government to strengthen public health security.” Paul Chaplin, president and CEO of Bavarian Nordic, said in a news release.1 “As a long-term supplier of Jynneos to the US biological preparedness, we are committed to continue supporting the government’s efforts to protect its citizens against current and future public health threats.”
Smallpox is a serious viral infection that often results in death. However, due to vaccination, there are no longer any naturally occurring cases in the world, with the last occurring in 1977, according to the Mayo Clinic. Patients are unlikely to come in contact with the infection naturally, and antiviral medication can now be used to treat the disease. Mpox can cause a rash similar to smallpox and flu-like symptoms and is currently endemic in parts of Africa. There are not any approved antiviral treatments for mpox, and research is still being done to determine appropriate treatment.2,3
The approval of the supplemental biologic license application was based on clinical data that demonstrated the comparability of both formulations for immune responses and safety. The current formulation is frozen liquid with cold-chain requirements, and the new formulations improve transportation, storage conditions, and shelf life for long-term stockpiling.1
In the study comparing the 2 formulations, 652 patients were split into 2 trial groups: the liquid-frozen and the freeze-dried formulations. A total of 651 patients completed the full analysis set, according to the study investigators. Most of the individuals had no detectable vaccine-related antibody titers prior to the first vaccination, and after the 2 doses, approximately 4 weeks apart, there were rapid increases of plaque reduction neutralization test (PRNT) and enzyme-linked immunosorbent assay (ELISA) geometric mean titers (GMTs) in both groups. The GMT peaked at approximately 6 weeks, or 2 weeks postvaccination.
The investigators noted that PRNT and ELISA seroconversion rates were above 85% at 4 weeks (after the first vaccination) and reached 100% in both groups at weeks 6 and 8.4
The GMT ratio of total antibodies was 0.8 at week 6, which investigators said showed noninferiority and equivalence of both formulations. PRNT GMT ratios were also similar at 0.824 at week 6. There was no difference in either group in T cell responses at any visit. As for safety, the majority of individuals reported at least 1 adverse event (AE), with 95.7% of individuals in both groups reporting at least 1 solicited or unsolicited AE.
Approximately 91.7% of participants in the liquid-frozen group and 93.2% in the freeze-dried group reported solicited local events, with pain, erythema, and swelling at the injection site being the most frequently reported. Solicited systemic AEs occurred in 55.7% and 57.1% of individuals, respectively, with the most frequent being fatigue and headache.4
