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The latest COVID-19 Omicron subvariants are expected to be in full force in the United States in the coming weeks and months.

They’ve been labeled with monikers such as BA.2.75, XBB, and BQ.1.

A new wave of COVID-19 Omicron subvariants is raising concerns among some health officials who say the latest mutations may drive a surge in cases this winter.

Officials say the new so-called “Scrabble subvariants” have already peaked in parts of Europe but are now on the decline. They are expected to arrive in the United States in the coming weeks and months as European nations tend to be 6 to 8 weeks ahead of the United States in terms of COVID-19 cases.

The new variants appear to be more contagious, but it’s uncertain yet if they will cause more serious illnesses. Officials say the latest Omicron strains may be able to evade many of the current treatments for COVID-19, but they believe the new Omicron-specific vaccine boosters can provide some protections.

Healthline asked two highly regarded experts on infectious diseases about these new variants and the concerns surrounding them.

Dr. Monica Gandhi, MPH, is a professor of medicine at the University of California San Francisco.

Dr. William Schaffner is a professor of preventive medicine at Vanderbilt University in Tennessee.

Schaffner: The COVID virus mutates frequently, so we expect to see new variant strains cropping up from time to time. The World Health Organization sponsors an international surveillance system that is designed to detect the appearance of variants early around the world. The newly recognized subvariants all seem quite contagious, so are beginning to spread. Fortunately, laboratory studies indicate that the new updated bivalent booster COVID vaccine still will continue to provide substantial protection against severe COVID disease caused by these variants.

Gandhi: These new Omicrons subvariants (like XBB, BQ 1, BQ1.1, BA2.75) are increasing in prevalence because of one of two reasons: increased transmissibility or evasion of antibodies or both. However, even if subvariants have more mutations in their spike protein and are more adept at evading antibodies, our immune system is fortunately “redundant” and doesn’t just rely on antibodies to protect us from infection. In fact, antibodies (such as IgA, which is the mucosal antibody most prevalent in the nose and mouth and IgG, which is the most prevalent antibody in the bloodstream) are our first line of COVID-19 defense in the nasal mucosa. Therefore, mild upper respiratory infections may become more common as these new subvariants evade our nasal antibodies. Luckily, the rate of severe disease should remain low in the United States due to the high amounts of population cellular immunity to the virus in the country.

B and T cells are our protectors from severe disease. Memory B cells — generated by the vaccines or as a result of a prior infection — have been shown to recognize the virus, including its variants. Specifically, if memory B cells see a variant, they are able to make antibodies adapted to the variant or subvariant. The vaccines or natural infection also trigger the production of T cells. While B cells serve as memory banks to produce antibodies when needed, T cells both help B cells make antibodies and help recruit cells to attack the pathogen directly.

Schaffner: It is hazardous to predict the behavior of COVID variants. Let’s wait and see and be prepared to respond.

Gandhi: All of these subvariants are still in the Omicron family, and we have luckily not had an entirely new variant since November 2021 (when Omicron first was described). In the United Kingdom, these subvariants rose and faded quickly, and the United Kingdom is often 6 to 8 weeks ahead of us in subvariant rises.

Gandhi: On August 31, 2022, the [Food and Drug Administration] provided emergency use authorization for two bivalent booster vaccines. Both mRNA vaccines have the genetic code for the ancestral SARS-CoV-2 strain but also include updated mRNA code for a shared component of BA4 and BA5, the latter being the most prevalent Omicron subvariant circulating in the United States. Especially if you are older, I would strongly recommend that you get the updated booster vaccine.

Schaffner: There is no doubt that the very best thing everyone can do to protect themselves, their families, and their communities is to be up to date in their COVID vaccinations with a special emphasis on receiving the new updated bivalent COVID booster, which is available to everyone who is 5 years of age and older.

Gandhi: Unfortunately, COVID-19 does not have features of an eradicable virus. Smallpox was successfully eradicated worldwide in 1979, not only because of the vaccine but because of some unique characteristics of the virus, including its lack of an animal reservoir, having clear pathogenic features that made it easy to quickly recognize the disease in sufferers, and a short period of infectiousness. Smallpox infection conferred natural immunity for life. SARS-CoV-2 has none of the features of smallpox that made it eradicable and is found in 29 species of animals, at least, which means we will always be dealing with COVID-19 in the medical system. With ongoing circulation, we will likely continue to see new subvariants but COVID-19 is becoming more predictable like influenza and not mutating as much.

Schaffner: There is no doubt that new variants will continue to appear. They will become variants of concern if they are so different that our current vaccines no longer will securely provide protection against serious COVID infection. We all hope this will not happen, but we must remain alert to this possibility.