The short shelf life of AstraZeneca’s COVID-19 vaccine is causing problems for the vaccine-sharing organization COVAX, which is co-led by the World Health Organization and focuses on getting jabs to the populations of poor countries.

The AstraZeneca vaccine has a shelf life of only two-and-a-half months, which often doesn’t allow enough time for countries that have infrastructure problems to quickly get the shots into the arms of its citizens.

Of the total expired doses reportedly declared by countries COVAX served during the week ending Feb. 6, by far the most — about 1.3 million — were from AstraZeneca, which is the second-biggest COVAX supplier after Pfizer.