• CDC director Rochelle Walensky said data suggests fully vaccinated people don’t carry COVID-19.
• On Monday, the CDC released a study finding mRNA vaccines 90% effective at preventing infection.
• Walensky also elaborated on the optimism and “impending doom,” she is feeling around the pandemic.
• See more stories on Insider’s business page.

Centers for Disease Control and Prevention Director Rochelle Walensky is touting new CDC data that suggests people who have been fully vaccinated almost never carry COVID-19. 

During an MSNBC interview with Rachel Maddow on Monday, Walensky said: “Our data from the CDC today suggests that vaccinated people do not carry the virus, don’t get sick, and that it’s not just in the clinical trials, but it’s also in real-world data.”

—The Recount (@therecount) March 30, 2021

Fully vaccinated people almost never test positive for COVID-19

Walensky was referring to a new CDC study of nearly 4,000 front-line workers, some vaccinated and some not, who tested themselves weekly for COVID-19 infections between December and March. 

Among fully vaccinated people in the study, there were only three “break-through” COVID-19 infections detected. In stark contrast, unvaccinated participants in the study logged 161 COVID-19 cases.

In other words, two shots of Pfizer or Moderna’s vaccines, followed by two full weeks for them to take effect, nearly zeroed out all detectable infections — including asymptomatic ones.

The CDC concluded, based on those results, that Pfizer and Moderna’s COVID-19 vaccines are roughly 90% effective at preventing COVID-19 infections in the real world, even the asymptomatic kind.

This is a great sign, because it means that vaccinated people likely don’t pose a risk of spreading the virus to those around them.

But more data is still necessary to say so definitively, which is why researchers are recruiting thousands of college students across the country to find out more about the likelihood of asymptomatic spread of this virus among vaccinated people. 

And the CDC walked back some of Walensky’s comments, telling the New York Times that the evidence “isn’t clear” and that the director was “speaking broadly.”

“We hope that within the next five or so months we’ll be able to answer the very important question about whether vaccinated people get infected asymptomatically, and if they do, do they transmit the infection to others,” Dr. Anthony Fauci, the nation’s top infectious-disease expert, said at a White House COVID-19 task-force briefing on Friday.

Walensky is still worried about a fourth surge because many Americans are not vaccinated yet, and variants are here

On MSNBC, Walensky also spoke about the challenges ahead for the country to exit the pandemic.

New, more transmissible virus variants are spreading fast, at a time when a majority of younger US adults have not been vaccinated yet. Walensky shared her fears about a forth surge on the horizon this spring.

“We’ve done so well in vaccinating the more senior members of our society that deaths might not be what we would expect with prior surges. It’s also the case, though, that if we don’t see those number of deaths, the deaths that we’re going to see is among younger people,” Walensky told Maddow. “Obviously we don’t want to see those either.”

Walensky elaborated on the “impending doom” she described in emotional remarks on Monday, remembering how dire the pandemic was just a few months ago.

“I’m watching the cases tick up. I’m watching us have increased numbers of hyper-transmissible variants. I’m watching our travel numbers tick up,” she said. “I have seen what it looks like to anticipate the oncoming surge. You know, we’re still losing people at 1,000 deaths a day.” 

Walensky stressed the renewed importance of getting shots into arms quickly now, not just to curb the spread of new variants, hospitalizations, and deaths, but also to tamp down on the potential for lasting effects of COVID-19.

“We know that about 10% of the population that gets sick with COVID has long-haul syndrome, has symptoms beyond three weeks, cardiac challenges, depression and mental-health challenges, pulmonary challenges, renal failure, clotting,” Walensky said.

Some long-haul COVID-19 patients are now finding that getting vaccinated can help them feel better after many months of such lingering issues.