Deadly blood clots have stopped completely since the under-40s were advised not to have the AstraZeneca Covid vaccine, experts have found.On May 7, the Joint Committee on Immunisation and Vaccination( JCVI) ruled that younger people should be offered an alternative jab because the risk of a dangerous clot outweighed the benefit.A nationwide team of British researchers who have been monitoring vaccine-induced clots since March said there had been a noticeable downturn in cases since the decision.