News Ontario reports first case of AstraZeneca linked blood clotting SHARE ON: Casey Kenny, staff Friday, Apr. 23rd, 2021 Photo provided by AstraZeneca The first known case of a rare blood clot linked to the AstraZeneca COVID-19 vaccine is being reported in Ontario. Officials say the case is in a man in his sixties who received his first dose of the vaccine. Just when he was inoculated isn’t clear. The man was treated and is recovering at home. Dr.David Williams, Ontario’s Chief Medical Officer of Health, says these cases are very rare and adds all vaccines in Ontario have been determined to be safe and effective by Health Canada.