U.S. infectious disease expert Dr. Anthony Fauci said Thursday that the United States is working to give additional COVID-19 booster shots to Americans with compromised immune systems as quickly as possible, as cases of the novel coronavirus continue to rise. The United States will join Germany, France and Israel in giving booster shots. U.S. regulators need to fully authorize the COVID-19 vaccines or amend their emergency use authorizations before officials can recommend additional shots, but the U.S. Centers for Disease Control and Prevention is working to make third doses available sooner under certain circumstances.

Fauci said rising cases resulting from the spread of the contagious Delta variant in the United States can be turned around with additional vaccinations. The seven U.S. states – Florida, Texas, Missouri, Arkansas, Louisiana, Alabama and Mississippi – with the lowest COVID-19 vaccination rates account for half of the country’s new cases and hospitalizations in the last week, the White House said on Thursday. Of those, Florida and Texas account for about a third of new coronavirus cases and an even higher share of hospitalizations in the country.

COVID cases are up about 43% over the previous week and daily deaths are up more than 39%, according to U.S. Centers for Disease Control and Prevention Director Dr. Rochelle Walensky. The United States hit a six-month high for new COVID cases with over 100,000 infections reported on Wednesday alone.