Scientists are reporting troubling signs that some recent mutations of the virus that causes COVID-19 may modestly curb the effectiveness of two current vaccines, although they stress that the shots still protect against the disease. … The research tested coronaviruses from the United Kingdom, South Africa and Brazil, and was led by Rockefeller University in New York with scientists from the NIH and elsewhere. A different, more limited study out Wednesday gave encouraging news about one vaccine’s protection against some of the mutations.