Rachel David is a Canadian television host, broadcaster, and journalist... (wikipedia)
We made assumptions about what these doses will be, knowing there is a relationship between the dose's active ingredient in the vaccine and how quickly you can produce it for a large number of people.
What we're testing in the trials is the dose that we need to use for the vaccine to be effective. The technology is tried and true but what we need to find out with this completely new strain is whether the doses we are using are effective.
The mutation that would make it spread from human to human, which is what we're worried about, is probably not enough to render the vaccine ineffective.