Yellow fever is running rampant in parts of Africa, so health organizations are attempting one of the largest emergency vaccine campaigns in the continent's history.
The World Health Organization has teamed up with other groups with the goal to reach over 14 million people.
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Yellow fever is usually spread by mosquitoes. And while most symptoms are mild, extreme cases can lead to organ failure.
The campaign is a response to outbreaks that have killed hundreds in the Democratic Republic of the Congo and Angola.
"This year with the Angola outbreak is the first time we've depleted the stock pile," said Alejandro Costa of the WHO.
Because an emergency vaccine campaign usually takes three to six months to plan — time WHO and other groups don't have — these vaccines are only about a fifth of a typical dose.
Other efforts — like spraying residents' homes to kill mosquitoes — are being carried out by other groups, like Doctors Without Borders.
