From the first report, to its characteristics (which make it the most contagious virus ever seen), passing from the data on vaccination efficacy and the “shield” of third doses. All the known properties of the variant and the unknowns about the future
When and where was it identified?
There Omicron variant it was first identified in Botswana on 11 November and in South Africa on 24 November. It is not known which country of origin of Omicron is, however, since the identification depends on the tracking capacity of the individual states.
What are its characteristics?
It has a distinctive combination of over 53 mutations that encompass nearly all of the mutations we know of from previous variants and more. In particular, it has 32 mutations in the spike protein (the part of the virus that most vaccines use to trigger the immune system against Covid). Recent studies have shown that it has evolved by optimizing mutations that evade the immune system.
Is it more contagious?
The World Health Organization (WHO) classified Omicron as a “variant of concern” (VOC) on November 26. Since then, in just over 2 months it has reached more than 110 countries, becoming dominant in many parts of the world, as happened in Europe and the USA.
It is estimated that it is 2 to 3 times more contagious than Delta: the cases of Omicron double every 2-4 days
(depending on the restriction measures).
According to some experts, Omicron’s R0 (r with zero), or the “basic reproduction number” which represents the average amount of secondary infections produced by each infected individual, could be equal to 10 (compared to 2.5 for the strain originally from Wuhan). It is assumed that it is the most contagious virus ever to appear on the planet.
Is it more lethal?
Several teams of scientists have found that Omicron infections most often cause mild illness compared to the previous variants of the coronavirus, with different values in the specific, but agree in substance.
A British study found that the risk of hospitalization is half that of Delta. It is not entirely clear whether this characteristic is intrinsic to the variant or whether it is due to the amount of vaccinated or cured population that Omicron encounters on its way, or to its “different biology”, which makes it more capable of reproducing well in the upper airways. and less well in the lungs.
Surely Omicron may still be serious in unvaccinated people.
Does Omicron escape rapid swabs?
The Omicron lineage has at least one advantage for diagnostic systems: it has a ‘deletion’ (at position 69-70) within the S gene that allows it to be detected by the molecular swab independently of sequencing (which serves as confirmation).
In general, rapid antigenic tests are capable of detecting Omicron (with the degree of error of these instruments). In practice, however, this margin of error implies a greater number of false negatives (people who are positive for Covid even if the test shows the opposite). This could also be due (in addition to errors in self-administration of rapid tests) to the fact that Omicron collects mostly in the throat and less in the nose and it may take longer for the virus to manifest itself in nasal samples. It is a hypothesis.
Do the symptoms change?
Based on a report published by the Uk Health Security Agency on January 14 and resulting from a large amount of data (about 180 thousand cases of Omicron and 88 thousand of Delta) sore throat is much more common and much less loss of taste and smell. Fever and cough are also more common in Omicron patients, while symptoms such as eye irritation or runny nose are less common.
Furthermore, the incubation time appears to have been reduced to 3 days, compared to 4-6 for the previous variant.
Does Omicron “hole” vaccines?
Every vaccine tested so far has lost of efficacy in neutralizing Omicron compared to other variants, especially in the ability to block the infection (the worst results were with AstraZeneca and Johnson & Johnson).
In Britain, researchers found that people who received two doses of the AstraZeneca vaccine enjoyed no protection from Omicron infection 6 months after vaccination. Two doses of Pfizer-BioNTech were only 34% effective, however, they still seemed to offer some protection from serious illness. In a large study of more than one million Covid cases, it was found that the risk of being hospitalized was 65% lower for those who had received two doses of the vaccine than for unvaccinated people.
Several studies also indicate that vaccine efficacy returns “very strong” (even against infections) after a booster injection (third dose or booster). In the aforementioned study of one million people, those who received the booster were 81% less likely to be hospitalized than those who were not vaccinated. The latest data on the effectiveness of third doses against Omicron are 50% against infections, 90% against hospitalizations and 95% against deaths. It is not known for how long.
Does Omicron “break” the immunity obtained with a Covid recovery?
Recent data from Great Britain, a country with a high vaccination rate (and a previously infected population as well), point to a 10% reinfection rate approximately, a sign that Omicron is different from the previous variants in order to partially evade the immunity obtained from a previous infection.
Researchers in the laboratory have estimated that the risk of reinfection with Omicron is approximately 5 times greater than that of other variants. A specific study ofImperial College of London on about 100,000 swabs taken in the first two weeks of the year shows that 65% of people recently infected with the Omicron variant said they had already had Covid before. Recent results from Denmark speak of a 3.6 times increased risk in the family compared to Delta (obviously the vaccination status of the people considered also affects these values).
There is still no data on how much and if it is possible to reinfect with Omicron itself or with Omicron’s sister widespread in some areas (see the question about mutations below) because too little time has passed since Omicron’s arrival (November in Africa, December in Europe): we usually talk about reinfection only 90 days after the last infection.
Do the monoclonals and other drugs used in the hospital work?
Most monoclonal antibodies used successfully with previous variants do not work with Omicron, with the exception of sotrovimab, manufactured by GSK and Vir.
For people hospitalized with Omicron infections, other treatments or drug combinations are also available. For example, there are remdesivir and dexamethasone.
The AstraZeneca monoclonal antibody, Evusheld, has just been authorized for distribution in Italy: the only preventative of the infection is intended for the very fragile, for those who cannot be vaccinated or for those with poor response to the vaccine. Effective against Omicron, it is given every six months.
Do antivirals work?
The only antivirals approved for Covid are the pills paxlovid (from Pfizer) and molnupiravir (from Merck). Preliminary experiments indicate that both treatments should work against Omicron. Their mechanism of action is regulated so as not to directly depend on the genetic mutations of the coronavirus. Just today Merk announced that data from 6 preclinical studies of molnupiravir indicated that it is active in vitro against the variant. In Italy it is already available, while paxlovid should arrive in February.
How did Omicron originate?
In an article on Naturethe experts of the Scientific Advisory Group for the Origins of Novel Pathogens (SAGO), the team of scientists commissioned by WHO to find out where Omicron comes from, have formulated three hypotheses: the virus would have accumulated mutations inside the organism of an immunocompromised person who was unable for a long time to get rid of the infection ; Omicron could be the result of a reverse zoonosis with a passage from man to animal and then again from animal to man; it would be a variant whose “missing links” (between Alpha, Beta, Gamma and Delta) have escaped monitoring.
Is it still changing?
There are three distinct sublines of Omicron (called BA.1, BA.2 and BA.3) and they all appear to have emerged around the same time. This means that Omicron had time to diversify before scientists knew it existed.
BA.2 shares 32 mutations with BA.1, but also has 28 unique mutations with, in all, 70 more mutations than the native Wuhan strain (omicron BA.1 has 53). This “sister” of Omicron is the one under examination because in some countries it is becoming prevalent: it has also been defined as “invisible” because it is difficult to identify, since it does not have the “deletion of the S gene” characteristic of Omicron BA.1: for to find it, therefore, it is necessary to sequence all the samples.
There is no evidence that the BA.2 variant causes more severe disease, the first studies fromImperial College they say that the vaccine efficacy against symptomatic cases is preserved, indeed slightly higher for BA.2 compared to BA.1.
However, it would be even more contagious and able to infect even more vaccinated people. This is what emerges from a study conducted in Denmark on over 8,500 Danish families between December and January. The researchers found that people infected with the BA.2 sub-variant were about 33% more likely to infect others than those infected with BA.1.
The arrival of BA.2 in some cases could slow down the descent of infections after the peak that has already occurred in many states.
Will specific vaccines against Omicron arrive?
Pfizer-BioNTech and Moderna, parent companies of the vaccine with messenger RNA technology, have announced the launch of specific clinical trials against Omicron. The first explained that they have already started the recruitment of volunteers, the second indicates the imminence of the administration of the first dose in the study that will start soon.
How has Omicron changed the course of the pandemic?
With such prodigious contagiousness, it is thought that many people will be reached by Omicron, probably the majority. The latest screenings ofInstitute for Health Metrics and Evaluation (IHME), an independent population health research center at the University of Washington Medicine, speak of the 60% of the population that will be reached by Omicron.
Some scientists think that as the spread of Omicron will lead to widespread (at least temporary) immunity and a rapid decrease in case growth, this phase should set the pandemic towards transitioning to endemic, characterized by a seasonal virus cadence and a portion of infected people more stable and constant from year to year.
It is only a hypothesis, however, that collides with many variables, first of all the possibility that the virus mutates in order to better escape vaccines and that the new variants may be less mild and / or even more infectious.
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