Blood clots are an extremely rare but serious side effect of AstraZeneca's COVID-19 vaccine, regulators announced on Wednesday. The benefits of AstraZeneca's vaccine still outweigh the risks, the European Medicines Agency (EMA) said in a press release. Still, the agency's safety committee said it's important to know the signs of a possible clot. A blood clot occurs when the blood thickens and forms a semi-solid mass. It can be a helpful response to stop bleeding in the case of injury, but these blockages can cause problems if they cut off blood flow to a vital area. Blood clots can cause...