Listen to the end. The Doctor cannot answer a caller's question at the end - "If you are so sure the vaccine is 100% safe, what is the point in stage 3 trials?" Doctor Pankhania does not answer the direct question at all.
I did not like this mini-debate. The Doctor kept going back to "you're not an expert." I think I would have had plenty of questions, and I am willing to bet my savings he would not have the answers.