First proof Covid jabs slash severe cases by up to 94% AND helps stop spread 22 Feb 2021, 15:30 Updated: 22 Feb 2021, 19:49 Invalid Date, COVID vaccines are slashing severe cases of the disease by up to 94 per cent - and helping to stop the spread, new findings suggest. Experts have today declared the results - the first evidence to come out of the UK's jab programme - as "very encouraging". �� 4 Prime Minister Boris Johnson will be assessing the effectiveness of vaccines to map the route out of lockdown. He is pictured holding a vial of an Oxford-AstraZeneca vaccine, February 17Credit: AFP or licensors In the first set of vaccine data published today, researchers in Scotland found the Oxford jab appeared to reduce a person's risk of hospital admission by up to 94 per cent - four weeks after the initial dose.