Vaccine supply is not keeping up with demand in many poorer nations.
Officials with the World Health Organization say the COVAX program has delivered 90 million doses to over 130 countries.
But that's not enough to protect populations from the virus. They say at least half of the low-income countries involved in COVAX don't have enough doses.
Some health experts reportedly believe it could take months or years to get enough people vaccinated worldwide to truly end the pandemic.