The researchers analyzed data from 9,544 mpox cases among men between the ages of 18 and 49 that were reported during July 31 through Oct. 1 from 43 U.S. jurisdictions. There was not a significant variation of efficacy between whether the vaccine was delivered intradermally — when a fifth of a dose is administered in between layers of skin — or subcutaneously, but to “optimize strength of protection,” eligible people should receive two doses, the researchers wrote.