The Food and Drug Administration says it will not require large-scale clinical trials for new formulations of COVID-19 boosters. The FDA made the announcement as a panel of experts said drugmakers should prepare vaccine boosters for the fall that are tailored to combat Omicron variant sublineages that are currently dominant in the United States. Nationwide, about 17% of coronavirus tests are coming back positive — the highest test positivity rate since a massive surge of COVID-19 cases last winter.