The American drug manufacturer PFizer said that there is no data proving that a single dose of its vaccine against the emerging corona virus will provide protection from infection after 21 days.
On Wednesday, December 30, 2020, Britain announced that it would change its vaccination strategy "to give the largest possible number of people at risk their first dose, instead of giving the two required doses in the shortest possible time." Some provinces of Canada do the same.
In response, Pfizer confirmed, in a statement published by the American site Axios, that although some protection seems to begin 12 days after the first dose, giving two doses of the vaccine - three weeks apart - is the only system. Which has been shown to be 95% effective in Phase 3 trials.
The company's warning comes at a time when many countries, including the United States, are discussing how to rapidly deploy vaccines in the most effective way possible.
However, the British government clarified, in a statement, that everyone will get their second dose, but after 12 weeks have passed from the first dose.
On November 9, 2020, the American company "Pfizer" and the German "Biontech" announced that they had reached an anti-Coronavirus vaccine that it was "90% effective."
Scientists believe that the Pfizer vaccine is one of the most effective vaccines, compared to the Chinese, Russian and British vaccines, with an effectiveness rate of more than 94%.