Concern is growing that the scramble for scarce supplies of monkeypox vaccines could see some nations and high-risk groups miss out — recalling the unequal global access to both COVID-19 vaccines and HIV medication.

The outbreak, which has reached nearly 100 countries outside of Africa, where the virus is endemic, is overwhelmingly being transmitted among men who have sex with men. They are getting priority for vaccination globally, but some face a longer wait than others.

"In a lot of ways we're seeing history repeat itself, unfortunately," said Wafaa El-Sadr, executive vice president for Columbia Global Centers, Columbia University's international network of campuses.