The vaccine hopes of millions of people worldwide are hanging on the Pfizer vaccine, but the supply of the shot is facing delays.

Why? Well, it relies on a whole lot of things that have never happened before all happening at once, in perfect sequence.

It's the first approved mRNA vaccine, it needs to be produced in the billions, and it needs to be kept at super-low temperatures until it's needed.

So today on Coronacast, Norman and Tegan discuss the challenges facing the Pfizer vaccine and what it means for our ability to protect the most vulnerable people in Australia.

Also on today's show:

* Some news outlets are reporting the vaccine that most Australians will get, the Oxford AstraZeneca shot, has efficacy of less that 10 per cent in elderly people. How worried should you be?