For now, the best way to prevent the current spikes from becoming a proper fourth wave is vaccination (which, even if cases continue to rise, can help prevent hospitalizations and deaths), increased surveillance, and a return to mitigation measures. Indeed, Los Angeles County on Sunday reinstituted mandatory mask-wearing in businesses and public areas, a major rollback after the U.S. Centers for Disease Control and Prevention said on May 13 that fully vaccinated individuals could shed their masks in many scenarios. Unless states can rapidly revive widespread and easily available testing, L.A. will be far from the last county to ask residents to mask up once again.