LONDON – The first 800,000 commercial doses of Pfizer Inc./Biontech SE’s COVID-19 vaccine are due to arrive in the U.K. over the next few days, after the Medicines and Healthcare products Agency (MHRA) became the first regulator to grant conditional approval. A total of 1,500 immunization centers in the U.K. are preparing to receive the vaccine, with administration now expected to start on Monday, Dec. 7.