A drop in Covid-19 cases can be deceptive, official warns. Here’s how the US can stay ahead of a variant-driven surge Although the rise of Covid-19 variants in the United States could spell trouble, pharmaceutical companies and scientists are confident vaccines will evolve with them, senior White House adviser Andy Slavitt told CNN. “I spoke to all the pharmaceutical companies and scientists, and they all say the same thing: Even if these vaccines diminish a little bit, they will be able to continually update them,” Slavitt, who is responsible for the Covid response, told CNN’s Chris Cuomo on Thursday.