A monoclonal antibody is a laboratory-produced protein that can potentially be used to treat sick patients as well as for prophylaxis. Fauci, the top U.S. infectious disease expert, described them as “precise bullets” that can be developed from antibodies from other people who’ve been infected and used as a treatment to fight the virus at multiple stages.

“What we really need are drugs that, when given early, can prevent a symptomatic person from requiring hospitalization or very dramatically diminish the time that they’re symptomatic,” Fauci said during the Facebook Live interview on Thursday. Monoclonal antibodies can be administrated intravenously or through a shot.

Fauci, director of the National Institute for Allergy and Infectious Disease, also said that the nation needs to “regroup” and “call a time out” as cases continue to surge across the U.S. Too many states skipped over certain guidelines as they jumped to reopen their economies.

“That is a recipe for getting into trouble,” Fauci said.

Zuckerberg, chief executive and co-founder of the social-media company, was critical of the government’s handling of the pandemic, saying “it’s really disappointing that we don’t have adequate testing, that the credibility of top scientists and the CDC are being questioned.”

Facebook has sought to remove misinformation on its platforms, but the struggle was illustrated during the event as several users’ comments scrolled next to the interview questioning the utility of vaccines. One pressed for “therapeutics or God created supplements.”

Fauci and Zuckerberg also discussed the importance of wearing masks, developing an effective vaccine, getting children back in school and young people’s role in stopping the spread of the virus

“Young people are intimately and heavily involved with what is going on with this pandemic,” Fauci said, pointing to the surge in younger people testing positive in the newest hotspots. “Consider your responsibility to yourself, but also the societal responsibility.”