The US National Institute of Allergy and Infectious Diseases (NIAID) announced in September 2022 that a clinical trial “evaluating alternative strategies for administering the JYNNEOS monkeypox vaccine” had begun enrolling participants. The intention is to assess the possibility of increasing the number of available doses. The trial will enrol more than 200 adults across 8 sites in the US.  


As we have previously explored, JYNNEOS is produced by Bavarian Nordic, a Copenhagen-based manufacturer. The vaccine is FDA approved for the prevention of smallpox and monkeypox in adults “determined to be at high risk”.  

JYNNEOS is approved for administration by two subcutaneous injections 28 days apart. However, NIAID reports that the FDA recently authorised intradermal administration to increase availability for distribution. This one-fifth approach is something we explored in our article on fractional dosing. Dr Fauci emphasised the need to “ensure we have an adequate supply” in order to “halt the global outbreak”.  

“NIAID’s trial of JYNNEOS will provide important information on the immunogenicity, safety, and tolerability of alternative dosing approaches that would expand the current supply”.  

As monkeypox cases continue to spread throughout the world the Centre for Disease Control and Prevention has reported 20,733 cases since May. NIAID suggests that “sexual transmission” is likely to be playing a significant role in this outbreak.  

Participation in the trial 

The trial is open to adults between the ages of 18 and 50 who have not previously been vaccinated against monkeypox or smallpox. The investigators are hoping to include a “demographically diverse group” that is reflective of the affected population.  

The study has three “arms”: 

  1. The first arm receives the standard, licensed regimen of subcutaneous administration. 
  2. The second arm will receive one-fifth of the standard regiment, administered intradermally. 
  3. The third will receive one-tenth of the standard regimen, administered intradermally.  

NIAID states that investigators will assess the peak immune responses induced. Research will take place over the course of a year, through 8 study visits. These involve physical examinations and blood samples.  

For more on the monkeypox outbreak and how we can respond, come to the World Vaccine Congress in Europe 2022.