The global number of weekly new cases of monkeypox reported to the World Health Organization (WHO) declined by 21% for the first time since the infection that has been endemic to central and west Africa began to appear around the world earlier this year.

Cases continued rising sharply in the Americas, however, in contrast to recent declines in European hotspots, WHO said in a report on Thursday showing 5,907 new monkeypox cases were reported in the past week, down from 7,477 new cases the previous week.

That is a dramatic reversal from the 20% weekly increases in reported new monkeypox cases over the past month. More than 45,000 cases have been reported in 98 countries since late April.

After four consecutive weeks of rising monkeypox cases globally, WHO says, the overall weekly decrease may reflect early signs of a declining infection rate in the European region but it will take time to see if that is sustained.

Monkeypox cases in the Americas were still rising sharply, accounting for 60% of all cases compared to Europe’s 38% in the past month.

WHO officials, meanwhile, say they are examining proposals to split scarce monkeypox vaccines doses to stretch supplies — a strategy adopted by the United States on August 10, in response to the global shortage of monkeypox vaccines.

As part of that decision released earlier this month, US Health and Human Services Secretary Xavier Becerra issued a 564 determination, granting the US Food and Drug Administration the power to issue an emergency use authorization for vaccines.

This gives the FDA permission to change the way the MVA-BN vaccine, made by Danish company Bavarian Nordic, is administered.

Group of monkeypox experts to examine the ‘fractional’ strategy

Dr. Kate O’Brien, WHO’s Director of the Department of Immunization, Vaccines and Biologicals, said a strategic advisory group of experts will meet at the beginning of October to evaluate “some of these fractional dose issues” and the evidence for and against the strategy.

Known as dose sparing, the U.S. fractional dose strategy splits the approved MVA-BN vaccine that is typically administered subcutaneously into five doses from each vaccine vial, and then delivers those “intradermally” just below the outermost layer of skin, known as the epidermis.

“The strategy of what’s termed using fractional doses for vaccines is not a new strategy for vaccines,” O’Brien told a virtual press briefing on Thursday.

“And we are looking really carefully at the evidence for the performance of these vaccines, these smallpox monkeypox vaccines,” she said, “to look at the equivalence or in fact, possibly the improved performance using fractional doses.”

Along with extending the limited vaccine supplies, the procedure is supposed to provoke a more powerful immune reaction.

But the strategy announced earlier by U.S. President Joe Biden’s administration is not going according to plan, Politico reports, with those administering the vaccine saying they’re getting only three or four doses out of each vial.

Other media have reported the intradermal procedure’s more frequent use on men of color who have sought the vaccine recently, while white men who got in line first for the jab were able to get a full dose in the more proven, subcutaneous manner. 

Another complicating factor is the requirement for health workers to get extra training for the delicate intradermal procedure.

The net result is speculation that if the outbreak continues to expand in the Americas, the US may be forced to fall back on another stockpile of ACAM2000 smallpox vaccines that are highly effective but can have dangerous side effects.