Many European nations—including France, Germany, Italy, Portugal, and Spain—recently paused the use of AstraZeneca’s vaccine due to alleged adverse reactions. The nations said they were waiting for the European Medicines Agency to declare the vaccine safe, which it did on March 18. But the decision to pause the vaccine’s use over concerns about rare blood clots may severely damage the continent’s vaccination efforts moving forward, just as the continent is experiencing a new surge in COVID-19 cases, says Bill Moss, executive director of the Johns Hopkins International Vaccine Access Center. Pausing was a “tragic” decision that likely strengthened existing vaccine distrust that will be even harder to diminish, he says.