People at risk for monkeypox who have not received a single dose of vaccine are 14 times more likely to get infected than those who have gotten a shot, according to the Centers for Disease Control and Prevention.

The preliminary data, collected from 32 states from the end of July through early September, is the first concrete evidence that the Jynneos vaccine is providing at least some protection against infection from the monkeypox virus circulating in the current outbreak.

“These new data provide us with a level of cautious optimism that the vaccine is working as intended,” CDC Director Dr. Rochelle Walensky told reporters during an update Wednesday.