The U.S. Centers for Disease Control and Prevention is stepping up efforts to track coronavirus mutations and keep vaccines and treatments effective against new variants until collective immunity is reached, the agency’s chief said.

The Covid-19-causing coronavirus is mutating while spreading around the world in the pandemic, but none of the mutations currently documented appears to be making the SARS-CoV-2 virus able to spread more rapidly, scientists said.

A roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for Covid-19, the illness caused by the virus.