“This is a two-dose vaccine, so people need to take two doses to be able to feel confident that they’re protected at 95% — 95% chance of being protected,” Bourla said during an International Federation of Pharmaceutical Manufacturers and Associations briefing on Tuesday. “At the dose one, it’s around 50%, something like that.”
Bourla added that from an epidemiology point of view, this is important because when a population starts having some type of immunity from the first dose, “that helps.”
“But again, I say, it’s a very big mistake if anyone tries to do it with only one dose when … with two, you almost double the protection,” he said.
Bourla's comments come after the United Kingdom became the world's first nation to begin vaccinating its citizens with a fully vetted and authorized Covid-19 shot —the Pfizer/BioNTech vaccine.