Pfizer Covid vaccine: what has the trial found and is this a breakthrough?

Early results from phase 3 trial look promising but there are still many questions to be answered

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Pfizer and the German biotech company BioNTech said on Monday that they had had encouraging early results from a phase 3 clinical trial of their coronavirus vaccine. The trial is assessing how well the vaccine works in preventing humans from becoming infected. Although details are scant, the news is positive.