Anthony S. Fauci, the man millions turn to for pandemic wisdom, displayed his trademark bluntness Thursday in an address to the medical community at Thomas Jefferson University, warning against premature hopes of “herd immunity" to COVID-19.

Speaking via Zoom to the Philadelphia institution’s faculty, staff, and students, he gave a crash course on the biology of the coronavirus and the latest medical advice on how to tackle it.

He steered clear of the various controversies surrounding him and President Donald Trump, the latest involving a campaign ad that featured Fauci’s words without his permission. But he issued a general warning about our polarized society, saying it may dampen public support for an eventual vaccine.

“There’s this divisiveness that’s going on in the country, epitomized by Washington, D.C., with so many mixed signals coming out that it’s difficult to put out a unified message,” he said.

The talk from Fauci, the director of the National Institute of Allergy and Infectious Diseases (NIAID), was billed as a “grand rounds” session — a type of educational forum common in academic medical settings. He spoke for 30 minutes at noon in his familiar Brooklyn-accented rasp, via Zoom, then took questions from a panel of Jefferson faculty and students.

Here are the highlights:

On progress with vaccines

John Zurlo, Jefferson’s chief of infectious diseases, asked Fauci why he projects that the vaccines might be 70% effective, rather than the higher levels of protection afforded by many other inoculations. Zurlo also asked Fauci to pick a favorite among the various kinds of vaccines now in development.

That drew a laugh from Fauci, for whom Zurlo worked years ago at NIAID.

“John, I sneeze and the stock market moves,” Fauci said. “I’m not going to tell you anything. I don’t even know. It would be foolish to predict what is going to be better. The proof is in the pudding.”

As for his estimate of how well the vaccines will work, Fauci said he based it partly on experience with other respiratory viruses such as the flu — for which vaccine effectiveness is often even lower. He said he does not want members of the public to expect a “knockout punch” from a vaccine and then be disappointed, possibly leading them to be less enthusiastic about getting it.

“I tend to be conservative in my projections of what’s going to happen,” he said. “I think we’ve got to set reasonable expectations. If I’m surprised pleasantly, so be it."

He predicted that by the end of November or December, scientists may have evidence of efficacy for at least one vaccine, setting the stage for public distribution in early 2021.

On herd immunity

Fauci alluded to renewed calls for “focused protection” — the concept of protecting older people and others who are most vulnerable to the disease, while easing restrictions for the rest of society.

Not a good idea, Fauci said. It remains a “puzzle” why some people get very sick yet most do not, and it remains difficult to predict which are which, he said. Genetics and previous exposures to viruses may both play a role. But physicians do know that certain underlying conditions place people at higher risk, such as obesity, and in the United States, that’s a large segment of the population, he said.

“We shouldn’t be lulled into complacency that this is only an old-person disease,” he said. “If you look at the general population, about 40% of individuals have susceptibility to severe COVID disease.”

He acknowledged that everyone wants to achieve “herd immunity" — the point at which enough people have immunity that society can return to normal. But the way to do that is with a vaccine, not by letting the disease spread unchecked, he said.

“We’re very concerned about this concept of letting people get infected, or letting herd immunity come in," he said. “A lot of people would have to die first before you got to herd immunity.”

On measures that stop short of ‘lockdowns’

Fauci sounded his familiar call for members of the public to continue with basic preventive measures. Wear masks. Stay at least six feet from those outside your bubble. Avoid crowds. Minimize time spent in indoor public spaces. Wash hands.

None of the above should be confused with a “lockdown,” he said.

“You can do this without shutting down the country. There’s a misunderstanding,” he said. “You can cautiously and prudently continue to try to open up the country and open the economy.”

On the latest treatments

Fauci reminded the Jefferson faculty of how the federal government is maintaining a running list of best practices for treating COVID, at covid19treatmentguidelines.nih.gov.

“It’s a living document that’s regularly updated,” he said.

It includes guidance for treating certain patients with steroids and the antiviral drug remdesivir, along with emerging evidence on drugs called monoclonal antibodies.

“There’s a lot of cautious optimism,” he said of the antibodies.

On how long we’ll need masks

Sandra E. Brooks, chief medical officer at Jefferson University Hospital, asked Fauci to predict how long masks and social-distancing will be needed.

Fauci said that if the vaccine is 70% effective, and if some people resist taking it, many months will elapse before society reaches herd immunity.

“You’re not going to have a profound degree of herd immunity for a considerable period of time, maybe toward the end of 2021, into 2022,” he said. “I feel very strongly that we’re going to need to have some degree of public-health measures to continue. Maybe not as stringent as they are right now.”

He added:

“It’s not going to be the way it was with polio and measles, where you get a vaccine, case closed, it’s done. It’s going to be public-health measures that linger for months and months.”