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COVID-19 spread from vaccinated to unvaccinated may already be happening in Dane County

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MADISON (WKOW) -- A day after the CDC announced new mask guidance based on new research that shows infected, vaccinated people could spread the Delta variant of the coronavirus to unvaccinated people, researchers at UW-Madison say that type of spread is likely happening here, too.

Professors Dave and Shelby O'Connor say that the new research shows vaccinated people who experience a breakthrough infection of the Delta variant carry high loads of virus deep within their noses.

"The same sort of really high amounts of virus in their system as unvaccinated people," Dave said. "That changes the rules from what we thought they were even just a month or two ago."

He says that means that the spread potential for someone infected and vaccinated, potentially even if they are asymptomatic, could be highly dangerous.

"Someone who's vaccinated and has a breakthrough infection, and is walking through a crowded building, is potentially going to be exhaling a lot of virus and is potentially going to be putting others at risk," he said.

The O'Connors say research in Dane County is pointing toward that kind of transmission likely happening here already.

"Here locally, we are also seeing some evidence that people who have breakthrough infections have, in some cases, these really high levels of virus that would be expected to contribute to spread within the community," Dave said. "That's something we have to be really, really worried about, especially as we get ready for kids to come back to UW-Madison next month and for K-12 kids to return to school."

Public Health Madison and Dane County is expected to release more information about exactly how this kind of spread is impacting our community Thursday.

Shelby O'Connor says this new discovery doesn't mean that the vaccines aren't working.

"The vaccines are still preventing those of us who are vaccinated from getting severe disease and ending up in the hospital," she said. "No matter what, if more people are getting vaccinated, there's hopefully fewer people in the hospital. And if there's fewer people in the hospital, our health system's not overburdened."

Experts have long held that the COVID-19 vaccines do not make you bulletproof -- rather, they prevent against the types of severe infection that land people in the hospital, or dead.

With the Delta variant now introducing this new mode of transmission through breakthrough cases in vaccinated people, the virus will now have more paths to reach unvaccinated people -- who are at an extreme risk of severe infection from the Delta variant.

"We may have more individuals walking around who are entirely asymptomatic with absolutely no reason to go get tested, who may actually be infected and they're carrying the virus," Shelby said.

The O'Connors say the uncertainty that comes with these new revelations, in conjunction with the rising case numbers and hospitalizations in Dane County, is why masking up again -- even if you're vaccinated -- isn't a bad idea.

"We don't know what we don't know right now," Dave said. "And if you see that the case numbers are increasing, day by day and week by week, as long as that's happening, there's something that's fueling that. And so you might say that the something that's fueling that only affects other people, but the first time you're wrong is going to be really painful."

The O'Connor's say despite our high vaccination rate in Dane County, the Delta variant was able to take hold very quickly -- leading to nearly all new cases being Delta -- which shows how much of a threat it is and emphasizes how quickly we need to stop the spread.

"Here in Dane County, we had 70 percent of our population vaccinated, and Delta took over in three weeks," Dave said. "That's because it has these different biological properties... That very fast turnover where things became Delta all of the sudden means that all of these things that are special about Delta are just now going to be hitting us."

Tuesday, Dane County health officials strongly advised everyone over age 2 wear a mask indoors. The CDC classifies Dane County as having "moderate" transmission, which is outside of the "substantial" or "high" categories federal officials recommended mask back up. Dane County officials said they made their recommendation because they did not want to get to a higher transmission category.