COVID-19. Omicron, the fashionable variant
The variants of the SARS-CoV-2 virus, which causes COVID-19, are now appearing in such a scheduled way that they remind me of the fashion shows that are held annually on the big international catwalks. The original strain, isolated in Wuhan, is now she gives the appearance of having been dressed in an ordinary, somewhat old-fashioned way, when compared to the racy garb of the Delta variant and, not to mention, the infectious version of the Omicron. It seems that the original strain has been forgotten and now we are waiting for the result of the competition between Delta and Ómicron; Which of them will become more infectious and manage to "infect" the attention of the viewing public? That was the unknown, which was resolved in less than a month and now Omicron is the isolated variant in 98% of new infections.
The Omicron variant, launched to the fore as recently as November 24, 2021, has arrived disrespecting all previous variants with its rapid conquest of the public in South Africa and, in a few weeks, the entire world. So let's see what Omicron has changed in the antigenic composition of his dress to gain such a competitive advantage over Delta.
In the figure on the left we can see the spatial structure of the “Spike” protein of the Delta variant (D) and the Omicron variant (O), where the yellow color represents the part of the protein that the virus uses to bind to the receptor. the cell and infect it, that is, the RBD (Receptor Binding Domain). The red dots represent mutations that the original "Spike" protein from Wuhan has undergone in the Delta and Omicron variants.
It is clearly evident that while Delta exhibits only 7 mutation sites in the “Spike” protein, compared to the original strain from Wuhan; the Ómicron variant shows 34 mutations in said protein and 15 of them are in the RBD, which is the point of the spear that the virus uses to infect us. Illustratively, while Delta has changed some of the embellishments on her dress, Omicron has made a radical change to her outfit!
dress, with 34 new modifications! How important are the new mutations present in Omicron in the context of its infectivity, its ability to evade the immune response induced by vaccines and, more importantly, its ability to cause severe symptoms and death? Let's see what we have been able to perceive from the behavior of Ómicron during his brief parade on the catwalk.
Regarding its infectivity, experts agree that the Omicron variant of SARS-CoV-2 may be more infectious than the virus that causes measles, the latter being the most infectious virus that we have been able to isolate and characterize. To appreciate the infectious potential of Omicron, let me make a comparison. Scientific evidence indicates that a person with measles can infect 15 other people, while a person infected with Omicron only infects 2.5 people. However, this comparison is misleading, because while the measles virus requires an incubation period of 15 days to become infectious, Omicron only requires 2 to 3 days! And if we apply a mathematical calculation, it is evident that
Omicron is the most infectious virus to ever walk the runway, thus far, and will probably take the title of being the most infectious the crowd has ever seen.
I don't know how to be in control of my mental health anymore.
— NotesFromTheShadows Mon Jun 21 10:29:00 +0000 2021
It is clear that the evidence shows that Omicron is more infectious than its predecessor Delta, managing to partially evade the immune system by nullifying the effectiveness of approximately 40% of the protective antibodies induced by vaccines, which immunize us with the "Spike" protein of the original Wuhan strain. So how do you explain the perception that such an infectious virus is less virulent than Delta and causes fewer hospitalizations and deaths? Perception, which may have negative repercussions regarding the strategies that we must adopt to face COVID, in its fashionable version in 2022. Be careful! Let us be aware that we are comparing oranges with apples, when comparing the impact of infection and disease induced by all the pre-Ómicron versions of SARS-CoV-2, which infected a population without any protection, with the infection-disease relationship induced by the Omicron variant that is infecting, for the most part, people already vaccinated and, therefore, protected from suffering of severe symptoms, require hospitalization or die.
Ómicron is infecting vaccinated people, because having a short incubation period makes the virus highly infectious and because the levels of protective antibodies that neutralize it, and are the first line of defense against symptomatic infections, decline over time in the blood and much faster in the respiratory tract. Fortunately, when antibodies decline, and no longer prevent infection, what really protects us from getting sick is memory cell immunity mediated by T cells that, unlike antibodies, continue to recognize the virus and eliminate infected cells regardless of the infection! variant that infects them, a less precise but very efficient reconnaissance!
Then we must consider the possibility that it is not that Omicron is a less virulent variant, but rather that since we are seeing its effects in an immunized population, it induces asymptomatic infection or with mild symptoms, consequently, few people end up requiring hospitalization. Both the virus and our immune system have adapted to each other, reaching a delicate balance of coexistence where, being vaccinated, we get infected, but we do not get sick. However, we should not accept as dogma that the Omicron variant is also less virulent when it infects unvaccinated people or older adults with weakened immune system and/or comorbidities. I want to be clear, in such people, there is still no scientific evidence that indicates without a doubt, that Omicron is less virulent. Being so infectious
It will surely infect susceptible people who will be at high risk of becoming ill with severe symptoms.
Observing Ómicron's behavior on the catwalk, it is also speculated that his appearance and permanence with a high infectious level will be transitory, marking the end of the pandemic, since by infecting vaccinated people it behaves like a "natural vaccine" with the version to the day of the protein "Spike" of Ómicron. From an immunological point of view, such a suggestion makes sense as it implies that the virus and our immune system are coming to a balanced understanding. On the one hand, the virus would be allowed to change the decorations on your dress in a moderate way and could infect us, but, on the other hand, the immune system would also be allowed to recognize it without much difficulty, allowing it to adapt quickly, conceding the infection, but avoiding the disease.
I want to be optimistic and I really hope that the appearance of Ómicron is the beginning of the end and that SARS-CoV-2 becomes an endemic virus that we will have to live with; but as I have been pointing out, this pandemic is an "experiment of nature" where we are the guinea pigs and, as a good scientist, I cannot blindly cling to a single scenario. As Professor Niels Jerne, Director of the Basel Institute of Immunology, Switzerland and 1984 Nobel Prize in Medicine, told me; "Humberto, think of 10 possible scenarios and choose one." I have to admit that this virus has given me respect and I still cannot choose what the final scenario will be, I really hope that this is "the beginning of the end of the pandemic" but, without ruling out the appearance of new variants in the future annual catwalks originated by virus replication, both in unvaccinated and vaccinated people. Let's continue to use preventive measures without letting our guard down!
