The Omicron variant of COVID-19 is not as deadly as the previous Delta variant, but that is no reason to grow complacent, Dr. Anthony Fauci cautioned on Wednesday.

Speaking at a public update on the Biden administration’s COVID-19 measures, Fauci referred to a series of preliminary studies of Omicron that he said shows the strain is less dangerous than Delta. The first he cited was a study from Canada that said the risk of hospitalization or death was 65% lower among people infected with Omicron compared to those infected with Delta.

Fauci also pointed to a second study that was from South Africa, which found that only 5% of infections from the Omicron wave resulted in hospital admission, versus 14% from Delta. In addition, it found that those hospitalized were 73% less likely to have suffered from severe effects when they contracted Delta.

Finally, Fauci turned to recent animal studies of mice and hamsters that found lung infections from Omicron appeared to be less severe than earlier strains. For all the positive takeaways that could be gleaned from these studies, Fauci cautioned that none of this should be taken as an excuse to become complacent.

“A certain proportion of a large volume of cases no matter what is going to be severe,” Fauci said. “So don’t take this as a signal that we can pull back from the recommendations.”

The U.S is experiencing a surge in COVID-19 cases and hospitalization, largely connected to Omicron but also due to winter conditions in some parts of the country. Several businesses and cities are scaling back plans to return to the office or to classrooms over the uptick, but there is reluctance in others to begin initiating new restrictions, let alone shutdowns.

A reopening of schools for a new semester has become a glaring concern as more children become hospitalized with COVID-19. According to the American Association of Pediatrics, the number of COVID-19 cases among children has reached its highest case count, with over 325,000 child COVID-19 cases since Dec. 30.

However, a number of mayors have been reluctant to return to remote learning arrangements for students.

President Joe Biden has said he supports keeping schools open.

“We have no reason to think at this point that Omicron is worse for children than previous variants. We know that our kids can be safe when in school by the way. That’s why I believe schools should remain open. They have what they need,” Biden said on Tuesday.