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Home » New COVID-19 BA.2.86 strain may evade vaccines and natural immunity

New COVID-19 BA.2.86 strain may evade vaccines and natural immunity

Last updated on December 7th, 2023 at 12:49 pm

A new COVID-19 strain, called BA.2.86, was first observed in July 2023. This new variant has caught the attention of public health officials because it may be able to evade immunity from vaccines or from the protection of a “natural” immunity.

I know that we get tired of hearing about what COVID-19 is doing, but if this strain is as infectious as the Omicron variant and avoids a person’s immune system, then we could be hitting another wave of this disease.

This article will review what we know and don’t know about this new strain of COVID-19.

young man in sleepwear suffering from headache in morning
Photo by Andrea Piacquadio on

What is this new BA.2.86 COVID-19 strain?

As I mentioned, it’s called BA.2.86, but it is also called the Pirola variant. It is related to the Omicron variant that was first identified in late 2021.

The CDC has explained that what makes the Pirola variant different is that it has over 30 mutations which means it may behave very differently than previous versions of the virus. That number of mutations is on par with what we observed with the Delta and Omicron variants of the original SARS-CoV-2 virus. The CDC said, “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.”

Other health agencies across the world have been closely monitoring BA.2.86. For example, the World Health Organization stated that it was a “variant under monitoring” on August 17.

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-19 hospitalizations.

We also don’t know whether this strain is more or less infectious (that is, the ability to spread from one person to another) than the previous strains.

So what we know right now is that it may evade an individual’s immunity, whether from vaccines or previous infection. And we don’t know if it’s more infectious or will cause more severe illness. We would all like the answers to these questions, but it takes time.

What do we know and not know about this new BA.2.86 strain?

The CDC published a risk assessment on BA.2.86, and here are the key take-home points:

  1. Cases — As of 23 August 2023, there have only been nine cases of individuals with BA.2.86.
  2. Severity — The CDC does not know the severity of the disease, but it is monitoring cases to determine if there is an increase in cases over time.
  3. Transmission — With only nine cases to work with, the CDC (and other public health agencies) will have a difficult time trying to determine how infectious this strain is. Yes, it is a conundrum since it takes a lot of cases to determine transmission rates.
  4. Immunity — Because of the large number of mutations in the BA.2.86 variant, the CDC states that it “raises concerns of greater escape from existing immunity from vaccines and previous infections compared with other recent variants.”
  5. Treatments — The CDC believes that currently available treatments like Paxlovid, Veklury, and Lagevrio will be effective against this variant.

I think it would be accurate to say that we don’t know very much at this time. But that’s a good thing about science, it works to accumulate data to prevent supportable hypotheses. And the CDC is being cautious but concerned.

What could happen?

Public health officials usually develop models for the spread of diseases. And of course, they have continued to model the spread of COVID-19 along with all of its variants and subvariants.

At this time, about 1800 people are hospitalized daily with COVID-19. That is almost 3X higher than the number of hospitalizations from the flu (which is around 100,000 per year in the USA).

New modeling from the CDC shows that the number of COVID-19 hospitalizations 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 estimate lands somewhere in the middle of that range, with daily hospital admissions of between 2,000 and 4,000 people by 18 September. Of course, the more we know about BA.2.86, it will greatly influence future models about COVID-19.

What about vaccines?

Because there have been only nine cases of BA.2.86, there are no data available that will tell us if the updated COVID-19 vaccines that are just now becoming available will be effective, or partially effective, against the new variant.

That being said, there has been plenty of data that has established that even when the vaccines did not prevent a COVID-19 infection, vaccines significantly reduced the risk of hospitalization from the disease. The reason for this is that even though vaccines may not give full immunity to a strain or substrain, they almost always provide partial immunity, which would be enough for the immune system to attack the virus before it leads to serious complications.

So, as I wrote recently, get the updated COVID-19 vaccine just in case this new strain gets moving fast.


It seems like we are often given limited information about COVID-19 and each of its subsequent strains. It’s because when we find a new strain, we have a limited number of cases to figure out what may or may not happen. I think the CDC and WHO are being extraordinarily cautious about BA.2.86 so that people are warned but not panicked.

So, what am I going to do? I have started wearing an N95 facemask again. From my observations, I’d say that about 10% of people are wearing masks in public places again. I will also be getting the updated COVID-19 vaccine in a couple of weeks, along with my seasonal flu and RSV vaccines.

Otherwise, don’t panic. But I’ll keep monitoring the situation and provide updates as necessary.

Michael Simpson
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