Rick West/The Associated Press Extremely rare cases of blood clots are hampering the rollout of two COVID-19 vaccines that Canada has purchased, as the country recorded its first case of the side effect from the AstraZeneca injection and the U.S. suspended use of the Johnson & Johnson version. On Tuesday, the United States temporarily stopped its use of the Johnson & Johnson vaccine while it investigates reports of a rare and severe type of blood clot in individuals who received the single-dose shot. Similar blood clots have also been reported after the use of the Oxford-AstraZeneca vaccine. Both shots use the same vaccine technology, called adenovirus vector.