Should all three of these candidates gain regulatory clearance, four countries—Canada, Japan, the UK, and the US—could vaccinate more than 100% of their entire populations based on the number of these three vaccines they’ve already pre-ordered. (Each vaccine requires two doses to generate protection from Covid-19.)

The scramble to pre-order vaccines helped spur their rapid development. Essentially, these orders allowed vaccine developers to take on the financial risk of clinical trials without knowing whether the candidate will work. In normal times, vaccine development can take up to a decade because companies are only able to pay for clinical trials once they have enough data to be confident it will be successful.

But it also creates a very real possibility that the vaccines will be unequally distributed. The Duke research group classifies as high or upper middle income the five countries and the EU that could potentially vaccinate more than their populations. According to mathematical models, if wealthy countries buy up all of the first available vaccines, the pandemic will actually kill more people than if these vaccines are distributed evenly across the globe.

Gavi, the Vaccine Alliance—an international consortium that includes the WHO and the Gates Foundation—has created the Covid-19 Vaccines Global Access Facility, or Covax, whose goal is to help distribute the rest of these vaccines across the globe. So far, they’ve received more than $2 billion in funding from countries, individuals, and philanthropic groups; they estimate that they’ll need an additional $5 billion to cover the rest of the world. Covax has so far pre-ordered 300 million doses of the AstraZeneca/University of Oxford vaccine and 200 million from Sanofi and GlaxoSmithKline (which is still in early stages of clinical testing), but those won’t be enough to cover the populations of the 92 countries that may need help buying them.

Correction (Nov. 25): An earlier version of this story showed twice the rate of vaccine coverage for countries in the second chart due to an error in data interpretation. We have updated the chart, and updated the story to reflect that only four countries, not six, currently have pre-ordered enough vaccines to vaccinate their entire countries.

Update (Dec. 1): This story has been updated with data of Mexico’s pre-orders of vaccines.

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