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Experts say new research on vaccinated people and COVID-19 transmission can help in establishing safety protocols. Willie B. Thomas/Getty Images
  • Some experts say that vaccinated people may be even less likely to transmit COVID-19 than previously thought.
  • That may be due to the viral load in a vaccinated person’s nasal passage as well as the way COVID-19 vaccines attack the coronavirus.
  • This information may be useful when determining safety protocols such as mask mandates.

COVID-19 transmission from so-called “breakthrough infections” may be significantly lower than was earlier suggested.

Experts say that they have looked at multiple studies on vaccinated people who’ve developed COVID-19 and have come to the conclusion that the Centers for Disease Control and Prevention (CDC) guidance on transmission from breakthrough cases may have been overstated.

That’s not because the CDC got it wrong, they add. Rather, the information is evolving as more people are vaccinated and studied.

Could this mean a change in safety protocols such as mask mandates?

Possibly, experts say. But not right away.

“People want a final word, a guarantee,” Ross Kedl, PhD, an immunologist at the University of Colorado School of Medicine, told Healthline.

“I’m sorry, but there are not any. But,” he added, “we do know what’s likely.”

What Kedl does see is definitive proof that the vaccinated who have the infection pass along much less virus than the unvaccinated.

Kedl began looking closely at the data around the topic before vaccines were approved. As a volunteer for Moderna’s phase 3 vaccine trial, he decided one day to swab his nose to see what he could learn.

It stunned him.

“I could not believe the amount of antibody,” he said.

Kedl explained that there’s “a bit of a sliding scale,” depending on a person’s medical background, their age, and the time since their vaccine.

However, he noted that his nasal swab showed him that while a vaccinated person with a breakthrough infection may have a high viral load in their nasal passageways, that viral load is diminished via the vaccine impact.

“What is abundantly clear is it’s less likely that a vaccinated person who is infected is going to pass this on,” he said. “Nobody wonders if this will be the case. The details are what we need to know.”

There are studies to back up Kedl’s assertions, including one on healthcare workers.

Kedl said the public needs to understand that infectious disease experts are far from muddling through all this and making changes willy-nilly.

Instead, he said, the public needs to know that decades — even centuries — of research have gone into this.

“People think we’re groping in the dark; seeing things we’ve never seen,” he said. “But we have years of concrete research. How did we get here? An appreciation of the last 150 years of vaccine study.”

Some things scientists knew included how and why vaccines work.

There’s also the impact of vaccines. Their purpose is, first, to save lives. Second, to cut down the impact of the virus on the person. And third, to eventually stall or stop the spread.

Scientists have also long known two things that play a role here: That the more immunity you have, the less the spread, and as immunity wanes, you do begin to spread more virus again.

In simple terms, the COVID-19 vaccine, Kedl said, works by coating the coronavirus with an antibody.

Kedl said that this information could be useful in establishing safety protocols.

“Is it meaningful enough to not, say, mask up if half the time you cannot spread it?” he asked. “I’d say no.”

But, he said, if your chances of spread are diminished to 10 percent, “which is my guess,” then perhaps strict precautions aren’t warranted.

Kedl said the fast wane in immunity we are seeing (and call for boosters) comes from the quickness in which the first two doses were given, something he said was necessary at the time because of the urgency to slow down hospitalizations and deaths.

Vaccines that are more spaced out last longer, he said. That’s why he expects everyone to end up needing boosters followed by a “flattening out” pattern,

“Once we have that, we should have increased freedom again,” he said.

“The data is already there,” he added, “for both the delta and original [variants]. It’s not a question of if it is true. It’s a question of what are we going to do with this?”

“The data accumulating shows that you can spread [the coronavirus after being vaccinated], no doubt,” Dr. William Schaffner, an infectious disease specialist at Vanderbilt University in Tennessee, told Healthline, “but less so and for a shorter time.”

Schaffner said that while we need to proceed with caution, the research gives him great hope.

“This really will result in less circulation of the virus among us,” he said, “pushing the virus down so it smolders rather than rages like a fire.”

The first task is getting the public to be on board with the science.

“It’s the people’s attitude — how they feel about this — that matters,” Schaffner said.

He points to the news that many Chicago police officers are threatening to resign rather than get vaccinated.

“We have not been able to penetrate that obstinance,” he said. “It’s ‘don’t tell me what to do.’ Of course, in society, we tell one another what to do all the time.”

Schaffner uses red lights as an example. Even when no other cars are there, he said, we all agree to wait for that green light.

Now, he finds himself having to help his public health students study the lay of the land when it comes to giving advice.

“That science is changing is completely normal to us,” he said, “but not at all for the general public. It’s a tricky discussion when you say ‘you cannot do this because of this,’ and then it changes.”

His hope? That more people come to understand how science works, as well as the years of research that have gone into vaccines.

Kedl said that the public needs to better understand how science evolves — something that’s not been expected of them in the past.

“We don’t always know what’s [for sure], but we do know what’s likely,” he said, “so we say we don’t know.

“A better communication may be, ‘we need you to do this now, but stay tuned,’” he continued. “We should say ‘It’s true and I’m not making this up.’ These are the most likely answers now. Could something change down the road? Yes, you have to give us that.”

Kedl wonders: If we’d been able to be more nuanced in messaging, could our vaccine rate have been higher?

“Some don’t like nuanced, but isn’t it better to hear what’s most likely?” he asked.

He hopes that as we learn more about the lower spread, that could lead to freeing the vaccinated from masks as well as pushing them to get a booster shot.

“Look,” he said, “if you want to protect other people, if that’s what you care about, get a booster.”