The CEO of the world's biggest vaccine producer, Serum Institute, warns that there will not be enough COVID-19 vaccines for the global population until 2024. Medical ethicist Art Caplan spoke with Boston Public Radio on Wednesday about why richer countries are getting the COVID-19 vaccine first.

"It's because the rich countries bought up the vaccine supply in advance, paid for it to guarantee they'd get it first," he said. "I'm not even sure that's totally wrong — taking care of your own country is morally defensible."

The debate arises once a country vaccinates its at-risk population, Caplan said. Should that country then share vaccines with at-risk gorups in other countries, rather than giving the vaccine to low-risk citizens?

"Then I think you've got to reconsider sharing the vaccine supply," he said. "But we have 200 million doses lined up that our government controls and (that) will go to use here. Those doses aren't going to Peru."

Art Caplan is director of the Division of Medical Ethics at the NYU Grossman School of Medicine.