CDC shares ‘pivotal discovery’ of Covid-19 superinfection that led to new mask directive

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Experts say vaccination lowers your likelihood of contracting Covid-19 in the first place – but for those who do, this data suggests they may have a similar tendency to spread it as unvaccinated people.

“Higher viral loads indicate an increased risk of transmission and have raised concerns that, unlike other variants, people vaccinated with Delta virus can transmit the virus,” Dr. Rochelle Walinsky, director of the US Centers for Disease Control and Prevention, said in a statement. Friday statement.

About 74% – or 346 cases – have been fully vaccinated. Of those cases, 79% reported symptoms. Genetically sequenced cases revealed that the delta variant was the main culprit.

The researchers found evidence that viral loads were similar between 127 people who were fully vaccinated and 84 people who had not been vaccinated, were partially vaccinated, or had an unknown vaccination status. Viral load is a proxy for how likely someone is to pass the virus on to others.

On Tuesday, Walensky reviewed these findings while disclosing guidance that people in areas with “high” or “significant” Covid-19 transmission should resume wearing masks indoors. More than 75% of the US population lives in these areas.

Walensky said Friday that the finding that the delta variant resulted in similar viral loads “was a pivotal finding that led to the updated CDC mask recommendation.”

“The masking recommendation has been updated to ensure that the vaccinated public will not inadvertently transmit the virus to others, including loved ones who are not immunized or who are immunocompromised.”

Questions remain

Before Delta, vaccination was known to influence factors likely to influence transmission. Not only did the vaccinated people tend to have lower virus loads, they also had milder symptoms and were sick for less time.

But research has shown that deltas spread more aggressively. Earlier this month, for example, Chinese scientists described viral loads that were about 1,000 times higher with deltas than with previous strains.

On Thursday, an internal CDC document said the delta variant was nearly as transmissible as chickenpox, while the early strain was akin to the common cold. This means that under certain conditions, an infected person may have passed on to two or three people, on average, early in an outbreak. But now, with delta, this number can be from five to nine.

“It’s one of the most transmissible viruses we know about. Measles, chickenpox, that — they’re all out there,” Walinsky told CNN late Thursday.

The CDC document also cited reports that the variant may cause more serious illness as well.

But even with similar viral loads, it is not certain that vaccinated people are as contagious as unvaccinated people.

Dr. Monica Gandhi, an infectious disease specialist at the University of California, San Francisco, who was not involved in the research said.

Gandhi said there are multiple parts of the immune system — including antibodies and T cells — that raise important questions about using viral load, which is measured by polymerase chain reaction (PCR) tests, as an indicator of how infectious someone is.

The new report says that “microbiological studies are required to confirm these findings” for similar viral loads among penetrating infections. It also notes that “asymptomatic penetrating infection may be underrepresented” because it is less likely to be detected.

Earlier this week, Walensky said ongoing investigations into the outbreak will help reveal more about what happens when this supernatural infection occurs.

“We are now continuing to follow up on those groups to understand the impact of these vaccinated people moving forward,” she said. “But again, I would like to repeat, we believe that the vast majority of transmission occurs in unvaccinated people and through unvaccinated people.”

More reasons to get vaccinated

Even with Delta, Covid-19 vaccines still reduce the spread of the virus. Furthermore, people who have been vaccinated are much less likely to end up in the hospital.

The Centers for Disease Control and Prevention (CDC) internal document estimates that vaccines reduce the risk of serious illness or death by 10 times or more, and they reduce the risk of infection by three times.

“Vaccination continues to prevent severe disease, hospitalization and death — even with Delta,” Walinsky said this week.

Of the Massachusetts residents in the latest study, none died and only five were hospitalized.

Of these five, one person was unvaccinated and had underlying medical conditions, and four were vaccinated. The ages of the vaccinated individuals ranged from 20 to 70 years, and two of them had underlying health conditions.

Additional infections were identified among visitors from at least 22 other states who visited the area from July 3 to 17. Thousands gathered for summer festivities, and infected people reported going to “crowded indoor and outdoor events at venues that include bars, restaurants, and guests’ rented homes.”

Although these findings prompted the CDC to update its guidance for areas with higher levels of virus transmission, the study notes that Barnstable County was not one of those areas until the outbreak. Between July 3 and 17, daily new cases rose from a 14-day average of 0 to 177 cases per 100,000 residents.

The study notes that “even jurisdictions that do not have significant or high transmission of COVID-19 may consider expanding prevention strategies, including concealment in indoor public spaces regardless of vaccination status.”

“The measures we need to get this under control — it’s extreme. The measures you need are extreme,” Walinsky told CNN late Thursday.

The study also notes that penetrating infections are to be expected, especially as the vaccinated population increases. “As vaccination coverage increases at the population level, vaccinated people are likely to account for a greater proportion of COVID-19 cases,” the authors wrote.

CNN previously reported an outbreak linked to Provincetown. In all, at least 882 cases have been linked to the group so far, about 60% of whom have been Massachusetts residents, according to local officials.

Provincetown manager Alex Morse told CNN Friday that the city appears to be taking a positive turn — with an indoor mask in place and the positive rate of testing declining.

“We think we’re heading in the right direction, but we’re clearly concerned about what’s happened here in the past few weeks,” Morse told CNN reporter John Berman.

A source familiar with the CDC’s decision to update its recommendations previously told CNN that in addition to the viral load findings, general delta spread and less-than-hoped-for vaccine uptake played key roles in the recent iteration of the directive.

CNN’s Elizabeth Cohen contributed to this report.

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