President Biden announced Monday that his administration will send at least 20 million doses of U.S.-authorized coronavirus vaccines abroad by the end of June, a decision that followed months of calls for the United States to do more to close the growing vaccine gap.

This is the first time the United States has agreed to share vaccines approved for domestic use, namely the Pfizer-BioNTech, Moderna and Johnson & Johnson shots. It will add to the 60 million doses of the AstraZeneca vaccine the country already pledged.

The decision to donate a share of the country’s considerable surplus signals the administration’s recognition that inequity in access may prolong the pandemic, as well as Biden’s desire to engage in the type of “vaccine diplomacy” that China and Russia have been touting for months.

But 20 million, or even 80 million, doses represent just a fraction of what experts say is need to end the pandemic.