Lower Doses of Jynneos Mpox Vaccine Proven Safe and Effective: Phase II Results

A recent Phase II trial, financially backed by the National Institutes of Health (NIH), has revealed promising results for a new vaccination method using Bavarian Nordic's Jynneos vaccine. The trial demonstrated that a reduced intradermal dosage of the vaccine can produce an antibody response equal to that of the full dosage.

The study's findings were shared at a significant event in Barcelona, where it was disclosed that administering a fifth of the standard Jynneos dosage resulted in a similar antibody production two weeks post the second vaccination, matching the full dosage's effect. However, this antibody level declined after a further two weeks, falling below the levels seen in the standard dosage group. The implications of this decrease are not yet clear, as stated by the NIH.

Participants who received a tenth of the standard dose exhibited a weaker antibody response throughout the study. The reduced dosage approach was found to be safe, with adverse events being similar across all groups and primarily mild reactions at the injection site. There were no serious side effects linked to the vaccine.

The research was facilitated by the NIH's National Institute of Allergy and Infectious Diseases. Jynneos is also under investigation for use in adolescents, with results anticipated later in the year.

In collaboration with the U.S. government, Jynneos was developed as a live attenuated vaccine to prepare the immune system against orthopoxviruses. It was granted approval by the FDA in September 2019, marking it as the first vaccine for the prevention of both smallpox and mpox.

During the mid-2022 outbreak of mpox in the U.S., Bavarian Nordic committed to supplying an additional 500,000 doses of Jynneos to the federal government. However, the company faced challenges in meeting the surging demand and sought external support to expedite its manufacturing processes.

In response to the urgent need, the FDA authorized the emergency use of Jynneos at a fifth of its standard dosage, administered intradermally. Recently, Bavarian Nordic has made Jynneos commercially available in the U.S., increasing its accessibility to patients and enabling reimbursement through public and private insurance providers.

Jynneos represents a significant advancement in vaccination strategies, particularly in times of outbreak and high demand, offering a potential solution to vaccine shortages while maintaining efficacy and safety.