Global gaps in access to COVID-19 vaccines are raising concerns that the continued spread of the coronavirus will breed more dangerous versions of the pathogen, weakening medical weapons and further crippling economies.

In a race to catch up with emerging coronavirus variants, wealthy countries are already benefiting from potent vaccines. While the U.S., Britain and European Union have given citizens about 24 million doses so far — more than half of the shots administered globally — vast numbers of countries have yet to begin their campaigns.

Disparities in immunity pose a threat to both have and have-not states. Giving the coronavirus an opportunity to advance and generate new mutants would have significant economic and public-health consequences, adding to the pain as the death toll surpasses 2 million.