Citing concerns there may not be enough vaccine supply, the National Institutes of Health is launching a clinical trial that will test whether smaller doses of the monkeypox vaccine, Jynneos, would be effective in protecting against the disease.

The focus on the new trial comes as monkeypox cases continue to rise, with more than 14,000 cases confirmed in the U.S. thus far. Globally, the number of cases has reached 40,000.

Currently, the Jynneos vaccine is emergency authorized by the Food and Drug Administration for intradermal injection, though it’s FDA-approved to be administered subcutaneously.

But in situations that echo some of the government’s early pitfalls in responding to COVID-19, federal agencies have struggled to secure a sufficient amount of Jynneos doses and will likely need months to gather enough in the Strategic National Stockpile.

As a result, finding out whether smaller doses of Jynneos administered through intradermal injection – “stretching” the vaccine supply, or “dose sparing” – would be effective in protecting people is an emerging priority. The approach would utilize a single dose vial of the vaccine for five separate doses, expanding the amount of people who can get a shot faster.

Scientific data around different routes of administering Jynneos, however, is still lacking. 

One study released in 2015 found that dose sparing is safe, but the new NIH clinical trial will investigate whether the approach will create antibodies at the same amount. The study will enroll some 210 people and will likely be held across some eight sites in the U.S. starting this month or in September.

In New York City, the local health department has already announced it plans to administer single doses for now to get the shot to more people as supply is low, despite the fact that the FDA has advised against it. The NIH data, which may not be available until December, will be crucial in understanding the best routes for administering the vaccine.

Last week, the Biden administration and the Department of Health and Human Services announced it had made an additional 442,000 Jynneos doses available for U.S. states. But there are likely up to 1.6 million people at risk of monkeypox who will need access to a vaccine.“FDA’s emergency use authorization of intradermal injection of the Jynneos vaccine is allowing us to get more doses to jurisdictions faster than anticipated and will help end this national monkeypox outbreak,” HHS Secretary Xavier Becerra said in a statement. “We will continue working with our state partners to ensure equitable and fair distribution of these vaccine doses to protect those most at risk and limit the spread of the virus.”