Moves by several countries to acquire supplies of Merck & Co.’s promising COVID-19 pill before it’s even approved are raising concerns that some poorer nations could be left behind in a repeat of the slow and inequitable rollout of vaccines.

A global initiative to deploy COVID-19 therapies like Merck’s molnupiravir is at risk of running into the same problems vaccine distribution faced, according to an independent report commissioned by the World Health Organization.

Merck to ensure access amid plans to substantially increase production capacity. Meanwhile, some wealthy and middle-income nations, including Australia, Singapore, Malaysia and Thailand, have followed the U.S. and have already secured molnupiravir or started talks to obtain it.