But, they say, data in recent weeks on new variants from South Africa and Brazil has undercut that optimism. They now believe that SARS-CoV-2 will not only remain with us as an endemic virus, continuing to circulate in communities, but will likely cause a significant burden of illness and death for years to come.

As a result, the scientists said, people could expect to continue to take measures such as routine mask-wearing and avoiding crowded places during COVID-19 surges, especially for people at high risk.

Even after vaccination, “I still would want to wear a mask if there was a variant out there,” Dr. Anthony Fauci, chief medical advisor to U.S. President Joe Biden, said in an interview. “All you need is one little flick of a variant (sparking) another surge, and there goes your prediction” about when life gets back to normal.