The UK will have to look "very carefully" at the effectiveness of a single dose of the Pfizer/BioNTech coronavirus vaccine, the country's chief scientific adviser has said.
Professor Patrick Vallance's comments came after reports from Israel suggested the protection it provides may be much lower than shown in trials.
Israelis began receiving first shots of the vaccine developed by Pfizer and its German partner BioNTech on 19 December last in one of the world's fastest vaccination roll outs.
Responding to Israel's claims that efficacy from the first dose of the Pfizer vaccine may be as low as 33%, Sir Patrick said studies showed that from day 10 after vaccination to 21 days and beyond, it was "much more like 89%".