For the trials of their vaccine, Pfizer used testing cohorts in the US and Germany for their phase 1/2 trials.Yeah alright. I've taken that onboard. That would explain where they could find 43,000 souls from. I asked a simple question and you have given me an answer. Good day to you.
For the Phase 3 trails, additional cohorts were used - in the US alone over 350,000 volunteered to be part of clinical trails for vaccines, with the Pfizer vaccine being trialed there, the UK and South Africa (for the latter it was selected due to the high infection rate, not relative wealth) with a cohort study of ages 16 to 85.