WARSAW, Poland - Countries across Europe resumed vaccinations with the AstraZeneca shot on Friday, as leaders sought to reassure their populations it is safe following brief suspensions that cast doubt on a vaccine that is critical to ending the coronavirus pandemic.The British and French prime ministers rolled up their sleeves, as did a handful of other senior politicians across the continent where inoculation drives have repeatedly stumbled and several countries are now re-imposing lockdowns as infections rise in many places.Britain is a notable exception: The outbreak there has receded, and the country has been widely praised for its vaccination campaign, though this week it announced that it, too, would be hit by supply shortages.