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CDC says vaccinated people unlikely to spread coronavirus

DENVER (KDVR) — New data from the Centers for Disease Control and Prevention shows that people who are fully vaccinated are unlikely to transmit the coronavirus to others.

The study focused on first responders and frontline health care workers who received Moderna and Pfizer vaccines, both of which use mRNA.


“It’s all great news and what we hoped was going to happen with vaccinations,” said Dr. Richard Zane, UCHealth chief innovation officer and emergency medicine expert.

The study is not complete. The data still needs to be analyzed, published and peer reviewed. But doctors across the country are optimistic.

“It’s scientifically intuitive and now we have hard evidence that it’s going to be true,” Zane said.

So why are doctors, public health experts and elected officials telling fully vaccinated people to coninue to wear masks?

“What I think everybody wants it to mean is that we can get rid of the masks. And it’s certainly a step in that direction,” Zane said. “We need a significant number of people to get vaccinated. We have to achieve herd immunity and then we can get rid of the masks.”

As of Thursday, more than 150 million vaccine doses had been administered in the U.S., with more than 16% of the population fully vaccinated against the coronavirus and another 29% halfway there, according to the CDC. Experts have said between 70% and 85% of the population must be protected to achieve herd immunity, a range that Dr. Anthony Fauci, the nation’s leading expert on infectious diseases, has recently cited.

“We haven’t factored in the variants into that equation yet,” said Dr. James Gaensbauer, a Denver Health infectious disease expert. “One of the challenges is that with the variants and the fact that some of the vaccines may not have quite a strong protection against the variant, we’re starting to see some of those estimates of herd immunity creeping upward.”

According to a recent Harvard report, some experts have raised the herd immunity estimate to near 90%.

“Each vaccine is a step toward getting back to normal,” Gaensbauer. “In the meantime, the CDC has interim recommendations for individuals who have completed their vaccine series, and it includes wearing a mask while in public, physical distancing, and avoiding large gatherings.” 

Gaensbauer added, “The CDC study evaluated the effectiveness of mRNA vaccines in real-world settings, and while the results are great news, we still are learning about how vaccines protect against transmission to other individuals and against new variants that are circulating.”