Why isn't more COVID-19 vaccine available immediately?

To truly control the pandemic, most people around the world need to be vaccinated against COVID-19. That's a tall order involving billions of shots.

By the end of this year, only about 70 million doses of the COVID-19 vaccines from Pfizer and BioNTech and from Moderna and the National Institutes of Health are expected to be shipped out worldwide. Next year, that number will jump to more than 1 billion. Other companies are also working on vaccines, but some populations still might not gain access until 2024.

In the meantime, the death toll continues to rise.

So why can't doses be pumped out and distributed faster?

Considering that vaccines can take years just