“But whereas AstraZeneca uses the same adenovirus for both doses, Sputnik V uses two different types, to prevent antibodies against the first dose from renderin

“But whereas AstraZeneca uses the same adenovirus for both doses, Sputnik V uses two different types, to prevent antibodies against the first dose from rendering the second one ineffective. (J&J only uses one dose; a trial of a two-dose regimen is ongoing.)”