Prince Harry and Meghan, the Duchess of Sussex, are renewing their push for COVID-19 vaccine equity, calling on Group of 20 (G-20) leaders to acknowledge that access to the shots is a “fundamental human right.”

In an open letter published Friday to world leaders at this weekend’s G-20 Summit in Rome, the couple, along with World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus, wrote, “When the leaders of the world’s wealthiest nations met at the G7 Summit in June, they collectively announced that 1 billion doses of COVID-19 vaccines would be sent to low- and low-and-middle-income countries to help vaccinate the world. Pharmaceutical companies have pledged almost the same.”

“Yet, as several nations still don’t even have enough vaccines for their own health workers, the world is left asking: Where are the doses?” the letter, posted on WHO’s website, said.

“Promises aren’t translating into vaccines reaching the people that need them,” Harry and Meghan wrote in their letter, which included support from Chelsea Clinton.

The pair — who stepped away from their official duties as full-time working members of Britain’s royal family and moved to Los Angeles last year — have been vocal proponents for global vaccine equity. They’ve appeared at several high-profile events, including last month’s Global Citizen Live, to promote vaccinations.

In their Friday letter, they wrote, “We understand that the pandemic recovery is nuanced and deeply complex, but we have a window of opportunity to come together as a global community and meet our humanitarian promises.”

“We can’t simply hope for the pandemic to end on its own. As the virus progresses through unvaccinated populations, we risk new and more deadly strains sweeping the planet,” they said. “Further, with trillions of dollars already lost and trillions more expected to be lost, economies will never fully recover until the whole world can operate as normal.”