Dr. Deborah Birx, the White House coronavirus task force coordinator, said Sunday on CBS News’ Face the Nation that it’s still unclear how long immunity lasts for those who have recovered from the coronavirus.

“In most infectious diseases, except for HIV, we know that when you get sick and you recover and you develop (an) antibody — that that antibody often confers immunity,” Birx said. “We just don’t know if it’s immunity for a month, immunity for six months, immunity for six years” in the case of COVID-19.

Researchers are still studying whether giving plasma from recovered coronavirus patients to sick patients can allow the antibody to offer protective immunity. And questions still circulate around vaccines and whether the antibodies produced are effective, Birx said.

“These are questions that we still have scientifically,” Birx added.

Vineet Menachery, a virologist at the University of Texas Medical Branch, previously told TIME that he estimates COVID-19 antibodies will remain in a patient’s system for “two to three years,” based on what’s known about other coronaviruses, but also that it’s too early to know for certain.

Birx also spoke on ABC News’ This Week Sunday about those protesting states’ stay-at-home orders. She emphasized the importance of official social distancing guidelines.

“What is your message to these protesters out there right now?” host George Stephanopoulos asked her.

“We’ve been telling the American people all along that they need to really follow state and local guidelines,” Birx said. “We’re not only protecting ourselves but we’re protecting each other when we follow the guidelines.”

The Coronavirus Brief. Everything you need to know about the global spread of COVID-19 Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Write to Sanya Mansoor at sanya.mansoor@time.com.