A safety monitoring system flagged that U.S. drugmaker Pfizer Inc (PFE.N) and German partner BioNTech’s updated COVID-19 shot could be linked to a type of brain stroke in older adults, according to preliminary data analyzed by U.S. health authorities. The U.S. Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) said on Friday that a CDC vaccine database had uncovered a possible safety issue in which people 65 and older were more likely to have an ischemic stroke 21 days after receiving the Pfizer/BioNTech bivalent shot, compared with days 22-44.