Check my maths...
Assuming 20,000,000 people to vaccinate, over eight months, March to October...
That requires 2,500,000 people per month to be vaccinated.
Assuming thirty days in a month, that requires 83,333 people PER DAY to be vaccinated.
OR
March to October is 245 days. 20,000,000 people into 245 days requires 81,632 PER DAY vaccinated.
Perhaps 20,000,000 is too ambitious?