Pfizer-BioNTech asked for authorization Friday to use their Covid-19 vaccine on 12-15 year olds in the United States. The companies said in a statement that they plan to make similar requests of other regulatory authorities worldwide in coming days. Their request to the Food and Drug Administration in the US comes after Phase 3 clinical trials of the Pfizer vaccine in 12-15 year olds were 100 pc effective in warding off the disease, according to the companies.