Former National Institute of Allergy and Infectious Disease director Fauci—who retired in December after half a century of public service—spoke to CNN over the weekend about the COVID pandemic.

He suggested that if cases surge over the coming autumn and winter months, people should consider using masks once again, particularly if health officials recommend it as a way of suppressing transmission of the virus.

“I am concerned that people will not abide by [masking] recommendations,” Fauci said. “We’re not talking about mandates or forcing anybody, but when you have a situation where the volume of cases in society gets to a reasonably high level, the vulnerable, the elderly, those with underlying conditions, are going to be more susceptible, if they do get infected, of getting severe disease leading to hospitalization. We know that. That’s a fact.”

His interview with CNN came as a new strain of COVID, BA.2.86—known as the “Pirola” variant—is identified in four U.S. states.

Fauci stressed in Saturday’s interview that mask mandates were not making a return—but he did remind CNN viewers that health officials still recommend masks be worn to reduce individual risk.

“I would hope that if in fact we get to the point where the volume of cases is such and organizations like the CDC recommend—the CDC doesn’t mandate anything—that people wear masks,” he said. “I would hope that abide by the recommendation and take into account the risk to themselves and to their families.”

Earlier this year, a scientific analysis of studies involving hundreds of thousands of people concluded that “wearing masks in the community probably makes little or no difference to the outcome of COVID‐19 like illness compared to not wearing masks.”

While the research team said in their paper that their confidence in the estimated effect of masking remained “limited,” Tom Jefferson, the Oxford University epidemiologist who led the Cochrane review, told journalist Maryanne Demasi there was “no evidence that masks are effective during a pandemic.”

“Makes no difference—none of it,” he said. “There is just no evidence that [masks] make any difference, full stop.”

Asked about the findings of the Cochrane study on Saturday, Fauci—who became the face of the U.S. response to the pandemic—said alternative studies had bolstered the case for using masks.

“When you’re talking about the effect on the epidemic or pandemic as a whole, the data [supporting masking] are less strong, but when you’re talking about it on an individual basis of someone protecting themselves, or protecting themselves from spreading it to others, there’s no doubt that there are many studies that show there is an advantage,” he said.

Several studies carried out at the height of the pandemic—including research from experts at Stanford Medicine and Yale University, the University of Edinburgh and China’s Jinan University—found that masking did appear to slow down the spread of the virus.  

According to the U.S. Centers for Disease Control and Prevention (CDC), a “layered” prevention strategy can help prevent severe illness from COVID-19. This means the best approach, according to officials, is taking multiple precautions—like staying up to date with vaccines and waring a well-fitting mask—to keep COVID at bay.

Pirola variant

Last month, the WHO said it was monitoring the spread of BA.2.86 because of the vast amount of differences between the variant and its predecessors, with the CDC following suit with its own announcement on the same day.

WHO has designated #COVID19 variant BA.2.86 as a ‘variant under monitoring’ today due to the large number of mutations it carries.

So far, only a few sequences of the variant have been reported from a handful of countries.
🔗 https://t.co/3tJkDZdY1V

— World Health Organization (WHO) (@WHO) August 17, 2023

In its preliminary risk assessment of the Pirola variant, the CDC said it appeared that existing tests and medications continued to be effective in the detection and treatment of the new strain.

While the organization said BA.2.86 may be more capable of causing breakthrough infections in those who had been vaccinated or previously infected with COVID, there was no evidence the variant was causing more severe illness.

“This variant is notable because it has multiple genetic differences compared to previous versions of SARS-CoV-2 and it has been detected in several locations within a short amount of time,” CDC officials said in an update on Aug. 30.

However, an updated version of the COVID-19 vaccine, which will be available to Americans in mid-September, is expected to be effective at reducing severe disease and hospitalization in those who catch the new strain, the CDC said.

“At this time, we don’t know how well this variant spreads, but we know that it spreads in the same way as other variants,” officials added. “If you choose to wear a mask, wear a high-quality one that fits well over your nose and mouth.”

According to the most recent CDC data, the Omicron EG.5 subvariant is currently the dominant COVID strain in the U.S., projected to account for around one in five U.S. cases of the virus.

Scott Roberts, an infectious diseases specialist at Yale Medicine, said in an article last week that while it was too early to determine whether Pirola would spread more easily than other variants or if it would even stick around, there may be a reason to worry: The number of mutations spotted in Pirola is similar to the number seen between Delta and its much more transmissible successor Omicron.

“When Omicron hit in the winter of 2021, there was a huge rise in COVID-19 cases because it was so different from the Delta variant, and it evaded immunity from both natural infection and vaccination,” he said. “The other concern is that this strain has been picked up in at least six countries, and the cases are unrelated. This suggests some degree of transmission in the [international] community that we’re not detecting.”

Veronika Matutyte, a medical doctor at the Lithuanian University of Health Sciences, told Fortune on Monday that masking was beneficial and remained especially important in poorly ventilated areas, healthcare facilities, or when community transmission was high.  

“With the presence of more contagious variants, masks provide a necessary adaptation,” she said. “Recent studies have shown that well-fitted masks with multiple layers can still offer good protection even against more transmissible variants.”