A top health official on Wednesday expressed enthusiasm about how many Americans are getting COVID-19 vaccinations every day, even as she and other federal officials warned people not to stop mitigation measures amid the pandemic. “I’m enthusiastic about the pace of vaccination that is happening, about the early data that we’re seeing, the changes in infection rates, the changes in emergency department rates,” Dr. Rochelle Walensky, director for the Centers for Disease Control and Prevention (CDC), said during a virtual briefing. But Walensky also added that she remains guarded and is worried about footage showing people enjoying Spring Break at various beaches and about people “who are not continuing to implement prevention strategies while we get fully scaled up.” “We’re at 13 percent. We need to be much higher than that to feel like we have adequate protection around this country,” she said, referring to the percentage of the population …