A cascading number of European countries — including Germany, France, Italy and Spain — suspended use of AstraZeneca’s COVID-19 vaccine Monday over reports of dangerous blood clots in some recipients, though the company and international regulators say there is no evidence the shot is to blame. AstraZeneca’s formula is one of three vaccines in use on the continent. But the escalating concern is another setback for the European Union’s vaccination drive, which has been plagued by shortages and other hurdles and is lagging well behind the campaigns in Britain and the U.S.