CNN  — 

Millions of Americans still need to get vaccinated to slow or stop the spread of Covid-19 and getting the pandemic under control could take “many, many” more vaccine mandates, Dr. Anthony Fauci said.

Fauci, the director of the National Institute of Allergy and Infectious Diseases, said if more people aren’t persuaded to get vaccinated by messaging from health officials and “trusted political messengers,” additional mandates from schools and businesses may be necessary.

“I believe that’s going to turn this around because I don’t think people are going to want to not go to work or not go to college … They’re going to do it,” Fauci told CNN’s Jen Christensen during an interview at the NLGJA, the Association of LGBTQ Journalists, convention Sunday. “You’d like to have them do it on a totally voluntary basis, but if that doesn’t work, you’ve got to go to the alternatives.”

The combination of the highly contagious Delta variant and the vaccine holdouts has put the United States in a “very difficult period” of the Covid-19 pandemic, Fauci said.

Of the eligible population in the US, which is currently limited to people 12 and older, 63% are fully vaccinated, according to data from the Centers for Disease Control and Prevention. Health experts and officials are aiming for the vast majority of the population to be inoculated to control the spread.

Last week, President Joe Biden announced vaccine requirements that include a mandate for businesses with more than 100 employees to require vaccination or regular testing for employees.

Businesses that want employees to return to work and stay at work will benefit from vaccine requirements, US Surgeon General Dr. Vivek Murthy said. The mandate will benefit employees as well, he added.

“I believe that will not only improve public health, but it will give people some more peace of mind,” Murthy told CNN Sunday.