London: Britain expects to have 10 million doses of Pfizer/BioNTech's candidate COVID-19 vaccine available by the end of the year if regulators approve it, Prime Minister Boris Johnson's spokesman said on Monday, following positive clinical trial results.The spokesman said that Britain had now ordered 40 million doses of the candidate vaccine developed by Pfizer and BioNTech, one of six that the government has agreed supply deals for.Pfizer Inc said on Monday its experimental COVID-19 vaccine was more than 90% effective, a major victory in the fight against a pandemic that has killed more than a million people, battered the world's economy and upended daily life."In total we have procured 40 million doses of the Pfizer candidate vaccine.