Slaoui said it would ultimately be up to the U.S. Food and Drug Administration as to how to evaluate the vaccine for U.S. authorization. "That first dose we think gives you somewhere around 50%, and you need that second dose to get up to 95%".
Health Secretary Matt Hancock told morning viewers in the United Kingdom that immunity from COVID comes two weeks after just one dose of the vaccine, which can be stored at refrigerator temperatures rather than a deep freeze like the other vaccines.
The Oxford vaccine has been found in trials to be less effective than the Pfizer shot but, crucially for countries with more basic health infrastructure, can be stored and transported under normal refrigeration, rather than supercooled to minus 70 deg C.
The government said in its announcement that the green light "follows rigorous clinical trials and a thorough analysis of the data by experts" at the regulator, the Medicines and Healthcare products Regulatory Agency, "which has concluded that the vaccine has met its strict standards of safety, quality and effectiveness".
As part of that effort, medical workers are to provide either of two approved vaccines: one from Oxford-AstraZeneca or one from Pfizer and BioNTech. That's different from BioNTech and Pfizer's messenger-RNA approach, which transforms the body's own cells into vaccine-making factories.
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However, Pfizer said that any "alternative" dosing methods should be tracked by health officials.
Early results from studies in nearly 24,000 people in Britain, Brazil and South Africa suggest the AstraZeneca vaccine is safe.
A United States nurse has tested positive for COVID-19 eight days after having received a Pfizer vaccine shot.
"Employers in the care sector must ensure there's paid time for staff getting the jab so they're not left out of pocket for doing the right thing to protect vulnerable people". Only 12% of study participants were over 55 and they were enrolled later, so there hasn't been enough time to see whether they develop infections at a lower rate than those not given the vaccine.
The British regulator approved AstraZeneca and Oxford's vaccine on Wednesday, saying a gap of three months between shots could boost its efficacy. World Health Organization experts decide whether or not the risks of a vaccine outweigh its benefits and then make a recommendation for the shots to be "pre-qualified" so they can be bought by donors for developing countries. The extreme-cold needed to store other vaccines is "very impractical" in developing countries, said Dr. Gillies O'Bryan-Tear.