As the U.S. and dozens of other wealthy nations began vaccinating their citizens against the coronavirus , developing countries where billions of people live had yet to even receive vaccine supplies. And although an international plan to send vaccines to more than 100 nations is kicking into high gear later this month, it will take years to implement with countless lives lost in the process and the global recovery from the pandemic significantly delayed.

Following the World Health Organizations approval of the AstraZeneca-Oxford vaccine on Monday, COVAX a joint effort by 190 governments and key international health programs will begin delivering hundreds of millions of doses of the shot to member states worldwide.

The nations, ranging from Indonesia to Nigeria and Brazil, are home to the vast majority of the global population. COVAX officials expect that 145 of those countries will be able to vaccinate around 3% of their citizens by the summer.

That still leaves billions without a jab that could protect them from severe illness, even as the coronavirus continues to evolve in unexpected ways and pharmaceutical companies continue to provide most of the vaccines they produce to rich nations.

The vaccine distribution has really been a story of have and have-nots, Niko Lusiani of Oxfam America told HuffPost.

In the U.S., for instance, all Americans who want a shot will be able to access one by the end of July, President Joe Biden said on Tuesday. Twelve percent of the population has already begun the process of vaccination, according to a Bloomberg tracker. And the U.S. is just the sixth in the world in terms of vaccinating its population, per The New York Times.

In comparison, as of last week, nearly 130 countries had not yet delivered a single dose of vaccine to their combined population of 2.5 billion people, the WHO said .

Amid a truly international crisis, governments are rejecting a united approach in favor of reinforcing inequalities on the basis of national citizenship. And that wont only hurt residents of countries that are slow to get the vaccine. Experts believe that a lengthy global vaccination process will prolong the coronaviruss grip on the globe. On Friday, a report in the medical journal The Lancet argued that the current inequitable distribution of vaccines leads to a greater risk of mutations that defy existing vaccines.