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New COVID strain may evade vaccines, alarming health officials


A new strain of COVID-19 that was identified only a week ago in the United States has prompted the Centers for Disease Control and Prevention to take the rare step of issuing a formal message that it could evade vaccines or the protection of natural immunity.

The strain is called BA.2.86 and is of particular concern because of its more than 30 mutations, which means it may behave very differently than previous versions of the virus. That number of mutations is on par with the difference between variants so serious that they were formally named, such as between Delta and Omicron, the CDC explained in the risk assessment issued Aug. 23.

Worldwide, health agencies are issuing a flurry of updates on BA.2.86. The strain only recently landed on the World Health Organization’s radar when it was named a “variant under monitoring” on Aug. 17. The CDC announced the same day that it had been detected in the United States.

Among the characteristics the CDC monitors for are how contagious a strain is, how well it responds to treatment, and how severely it affects people.

“BA.2.86 may be more capable of causing infection in people who have previously had COVID-19 or who have received COVID-19 vaccines,” the CDC risk assessment stated.

The agency is evaluating how well the forthcoming updated vaccine, due out in September, performs against BA.2.86.

A new forecast also released this week by the CDC predicts hospitalizations due to the virus will continue their upward trend through at least mid-September. Currently, about 1,800 people are hospitalized daily with COVID-19. The new prediction shows that number has a small potential to drop as low as 1,100 daily, but it could also increase by as many as 7,500 per day. The most likely scenario lands somewhere in the middle of that range, with daily hospital admissions of between 2,000 and 4,000 people by Sept. 18.

The CDC said there is “no evidence” that BA.2.86 is causing more severe illness but said that could change as more information becomes available. Health experts typically gauge severity by the rate of COVID hospitalizations.

The journal Nature reported that many scientists see similarities between the emergence of BA.2.86 and that of Omicron, which rapidly spread around the world in late 2021.

“There’s a little bit of déjà vu all over again,” University of Michigan virologist Adam Lauring, MD, PhD, whose lab detected one of the first U.S. cases of BA.2.86, told Nature.

Dr. Lauring, as well as the CDC and the WHO, all caution that more data is needed to truly understand the threat posed by BA.2.86.

“There’s good reason to think it won’t be like the Omicron wave, but it’s early days,” Dr. Lauring said.

A version of this article first appeared on

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