Most doses of Bavarian Nordic’s two-dose Jynneos monkeypox vaccine administered in the United States have been first doses, U.S. Centers for Disease Control and Prevention Director Rochelle Walensky said on Friday.

Monkeypox cases in some large U.S. cities appear to be declining, matching trends seen in Europe, and experts are cautiously optimistic the outbreak may have peaked in places hit hardest hit by the virus.

More than 41,000 cases of monkeypox and 12 deaths have been reported from 96 countries, with the majority of cases from the United States, the World Health Organization said on Thursday.

Bavarian Nordic, the maker of the only approved monkeypox vaccine, said on Wednesday it was exploring the viability of using technically expired doses to help bridge a growing gap between demand and supply due to the current outbreak.

Switzerland plans to procure 40,000 doses of monkeypox vaccine as well as 500 units of an antiviral drug, the government said on Wednesday.

The British scientists behind one of the major therapeutic COVID-19 trials have turned their focus to treatments for monkeypox, a viral disease that has been labeled a global health emergency by the World Health Organization (WHO).

A reliance on vaccines in short supply and questions over their best use are hampering efforts to curb the global spread of monkeypox which has hit dozens of countries for the first time, health officials say.

Danish biotech firm Bavarian Nordic said on Thursday it has signed up a U.S.-based manufacturer to package its Jynneos monkeypox vaccine and the production is expected to begin later this year.

The United States will boost its supply of monkeypox vaccine by making an additional 1.8 million doses of Bavarian Nordic’s Jynneos vaccine available for ordering starting Aug. 22, the White House said on Thursday.

Cases of monkeypox are growing at an alarming rate and Bavarian Nordic, the company that owns Jynneos, one of the two approved vaccines, may no longer be able to keep up, according to a report by Bloomberg.