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CDC Expected to Again Recommend Indoor Masking, Even for Some Vaccinated People

Federal health officials will recommend Tuesday that even people who’ve had their COVID-19 shots wear masks in indoor settings in some places, a major setback in the progress in the U.S. epidemic that reflects a surging coronavirus variant and the country’s ongoing struggles to increase vaccination rates.

The expected change to the Centers for Disease Control and Prevention’s earlier guidance, reported by several media outlets, comes as the Delta variant — the most transmissible version of the pathogen yet, by far — is igniting outbreaks and driving hospitalizations up in states with low vaccination rates, like Missouri, Arkansas, and Florida. The variant is also responsible for seemingly increasing numbers of breakthrough infections.

The guidance will apply to geographic areas with high transmission rates, NBC reported.

CDC Director Rochelle Walensky is slated to brief reporters Tuesday afternoon.

Just two months ago, the CDC said that fully vaccinated people no longer needed to wear masks indoors, citing evidence that the immunizations prevented many cases entirely and left those who still got infected “less likely to … transmit [the virus] to others.

But in addition to spreading more efficiently, Delta seems to have at least some ability to evade the immune response people generate after being vaccinated. Multiple studies have indicated that immunized people are still broadly protected against severe COVID-19 and death, but there is emerging evidence that Delta can cause breakthrough cases at higher rates than other virus versions.

Delta’s general transmissibility stems at least in part from changes in its genome that allow it to build up much higher levels of virus in the upper airway, leading to people emitting more virus for longer periods of time, meaning they are more likely to infect others.

An administration official, speaking on the condition of anonymity, told STAT that health experts do not have studies proving that fully vaccinated people are transmitting the virus. Rather, the official said, the updated guidance is based on studies showing that vaccinated people who contract the Delta variant also had high levels of virus in their airways, which suggested that they may be infectious to others. With other variants, vaccinated people had substantially lower levels of virus in their noses and throats compared to unvaccinated people.

The new masking guidelines provide an unwelcome turn in the pandemic. As vaccines started rolling out, it was clear they weren’t just protecting people from getting so sick they needed hospital care or they would die, but that they were also drastically cutting transmission.

It’s taken some time for scientists to tease apart all that Delta can do in vaccinated people. Most concerningly, it has been ripping through unvaccinated populations, leading to another surge in hospitalizations in some states that are almost entirely among people who haven’t been immunized. Experts are still trying to determine if Delta causes more severe disease on average than other variants.

But recent infection clusters that included vaccinated people — and that broadly caused mild and asymptomatic cases — raised worries that Delta was potentially spreading among vaccinated people to an extent.

Vaccinated people passing the virus to other vaccinated people isn’t ideal, but given how protective the shots are against the worst outcomes, the bigger concern right now is that vaccinated people could be contributing to the spread of the virus to unvaccinated people. Vaccinated people could also be transmitting the virus to individuals who didn’t mount robust responses to the shots because their immune systems are suppressed, including some with cancer or who have received organ transplants.

It’s unclear how the new CDC guidelines will land with an American public that seems eager to move on from the pandemic, even if the pandemic is not done with them. Many people who are vaccinated feel like they’ve done their part and might be unwilling to take a step back. And while health officials hope they can persuade some of the remaining unimmunized people to roll up their sleeves by improving access or addressing concerns, some portion of people have cemented their resistance to the shots.

Under the previous guidelines, unvaccinated people were still supposed to wear masks in public indoor settings.

The CDC says breakthrough cases still appear to be rare given how many people have been vaccinated, and the vast majority of infections are asymptomatic or mild. It’s also thought that because so many of those cases are so tame, many go undetected. However, many experts argue that breakthrough infections that cause no symptoms shouldn’t really be considered as cases. Mild or asymptomatic breakthrough infections are signs that the vaccines — whose top aim is to stave off death and severe illness — are doing their job, experts stress.

This story was originally published by STAT, an online publication of Boston Globe Media that covers health, medicine, and scientific discovery.

Copyright 2021 KQED