New COVID 19 Variant: Arcturus (Omicron XBB.1.16) Increasing. What’s the Significance?
In this video, Dr. Seheult of MedCram discusses the latest new Omicron subvariant named Arcturus. This variant has been found in 22 countries around the world but recently has been discussed in the news due to rising cases in India. It is known as Omicron XBB.1.16.
Is this variant more dangerous?
From the data thus far, this new variant has not been found to have any significant change in severity. It is noted to be 1.2 times more infectious than prior variants and its symptoms include cough, fever, sore throat and conjunctivitis. The conjunctivitis is new finding compared to prior infections from Omicron.
How many people are dying due to this variant?
Currently based on the data it looks like for every 100 cases of COVID-19 there is approximately 1 death associated with it. At the present time it appears that in India the number of new cases of COVID-19 per 1 million is 3.5. If the death rate was continuing at 1 per 100 persons we would expect to see a death rate of 0.03; however, it currently shows that new deaths are only at a level of 0.01 new deaths per 1 million. We are fortunately not seeing the same rise in deaths as previously. Officially, India is also not reporting a significant rise in new deaths. This variant has been found in the US and Canada for several months and has not grown to much prominence in terms of the number of hospitalizations and deaths. It does not appear to be of much alarm at this time. However, India is taking precautions and in some areas is reinstituting masks and warning healthcare professionals in India to be prepared for a possible surge.
How does the immune system work with COVID-19 variants?
Dr. Seheult goes on to discuss the immune system and how it relates to future COVID-19 variants. There was an article published in Scientific American discussing how your immune system evolves to fight Coronavirus variants. It goes into great detail about the immune system and Dr. Seheult wanted to explain why it is that you can have a reduction in efficacy of preventing cases but not so much so in hospitalizations and deaths. He also discusses recent health data about the benefits of vaccinations and how even to this day the benefits may still be holding up.
B cell response
In a normal SARS-Cov-2 infection, macrophages ingest the virus and then the protein pieces of that virus are put on the surface of the macrophage and it becomes an antigen presenting cell that B cells respond to. The body makes B cells against these antigens, and they are primed to make antibodies.
Antibodies are only one tool in the immune system. The body can also use interferons which can be augmented with hydrotherapy and fever. These interferons can be used in any type of infection and are not affected by mutations. This is one arm of the innate immune system.
Another arm is called the adaptive immune system and antibodies are just one way that the adaptive part of the immune system has to work against these viruses. Some B cells will produce a perfect fitting antibody to an antigen. But as time goes on and the virus mutates, these B cells will then no longer be as close fitting as they once were. This would happen whether or not you were or weren’t vaccinated. The immune system also while making the “tightly” fitting antibodies to antigens, makes some B cells that are more loosely fitting to the original antigens. These antibodies may at some point fit more tightly to antigens that mutate in the future. This allows for a broad response.
T cell response
When the virus attacks a regular cell and the body has to eliminate that cell, this is often what causes a person to need to be hospitalized. The T cell response to removing the infected cells can become so hyperactive that the resulting inflammation can be overwhelming and cause fluids to fill up in areas such as the lungs. In a cell that has been infected by a virus, the viral proteins get chopped up and and are attached to a cell protein known as a major histocompatibility complex (MHC) class 1 and get placed on the surface of the cell and these signal cytotoxic (killer) CD8 T cells to come in and destroy the cell. These CD8 cells dock with the MHC proteins and recognize the viral protein fragments. The T cell response is even more broad than the B cell response. The response from the T cells is broad enough so that mutations in the spike protein will not affect the T cell response. It is the T cell response that is important for preventing hospitalization and death. It is most likely that due to the T cell response we are not seeing ongoing surges in the hospitalizations and deaths as the virus continues to mutate.
What is public health data showing?
Looking at some real life data, Dr. Seheult looks at the public health department of Utah. He reviews the cases, hospitalizations and deaths amongst unvaccinated, fully vaccinated with 2 doses and bivalent boosted individuals. The cases will be reflective of the B cell response whereas the hospitalizations and deaths will be more reflective of the T cell response. In unvaccinated individuals compared to individuals who were vaccinated with 2 doses of vaccine there is a 1.4 greater risk for testing positive for an infection. Even despite Omicron and the newest variant, because the B cells can mutate in some way there is still a reduction in cases amongst those who have been vaccinated. For the reduction in hospitalizations and deaths, there is an even larger decrease between those who are vaccinated and unvaccinated. This is because the T cells’ broad response to the virus after vaccination. Those who were bivalent boosted had an even larger decrease compared to those who were unvaccinated. As the unvaccinated population becomes more and more infected you should start to see a diminishing of the differences between the vaccinated and unvaccinated population. As the benefits of new boosters and vaccinations change it will need to be evaluated in the overall equation as to risk vs benefit of getting future boosters.
LINKS / REFERENCES:
Virological characteristics of the SARS-CoV-2 Omicron XBB.1.16 variant (CSH) | https://www.biorxiv.org/content/10.11…
Your Immune System Evolves to Fight Coronavirus Variants (Scientific American) | https://www.scientificamerican.com/ar…
Vaccination Status (Utah) | https://coronavirus-dashboard.utah.go…