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Home SCIENCE Omicron seen as a milder coronavirus, but scientists aren't sure

Omicron seen as a milder coronavirus, but scientists aren’t sure

For more than two years, Cathy Baron and Sara Alicia Costa managed to avoid the coronavirus. But despite being fully vaccinated and reinforced, the Omicron variant finally caught up with them.

Baron is an actress and dance instructor who lives in Santa Monica. Costa is an architect in Austin, Texas. They are both 40 years old and healthy. But the two friends saw two very different sides to the variant, which they hoped would be smoother than previous strains.

For Costa, the Omicron variant lived up to its reputation for mildness, causing headaches and “something like a horrible cold” for a couple of days. She was visiting Baron and surfing in Santa Monica a week after testing positive.

Baron’s illness was deeply distressing. She was crushed for several days with a high fever and debilitating muscle aches, and she was too tired to teach her pole dance class for three weeks. Two months later, she is still dealing with episodic fatigue, brain fog and coughing fits.

Baron and Costa are what scientists would rule out as an “n of 2”. If his experience were a study, the sample size would be too small to draw conclusions, especially one as important as whether the Omicron variant really is less virulent than the SARS-CoV-2 variants that preceded it.

And yet, their contrasting experiences are as revealing as many of the research studies to date that have tried to determine just how dangerous Omicron is.

“It’s an excellent question,” one that many researchers think they know the answer to, he said. dr Stanley Pearlman, a virologist at the University of Iowa and a leading coronavirus expert.

“I think it’s true” that the Omicron variant is causing milder illness, he said. But the picture is “unclear,” she warned.

Omicron came to the United States at a time when 60% of Americans were protected by COVID-19 vaccines and approximately one-third of Americans (including some who had been vaccinated) had already been infected with the coronavirus. Not only was there a high level of population immunity, but those who got sick had access to treatments that were not available to people sickened by the initial strain from Wuhan, China, or the Alpha and Delta variants that followed.

Perhaps these are the reasons why people infected with Omicron have tended to experience milder illness.

“Omicron is widely said to be inherently less pathogenic, but there is no real evidence for that,” he said. dr Christopher Chiu, a COVID-19 researcher at Imperial College London.

“Comparisons with Delta are like apples and oranges,” he said. “Delta was circulating at a time when many were not yet vaccinated or previously infected. Rather, Omicron is largely causing advanced infections in people who already have partial protection from immunity conferred by vaccinations or infection.”

Since its appearance in November, researchers have seen that compared to previous variants, Omicron was less likely to send infected people to the hospital or to the grave.

First in South Africa and then in communities across the United States, the new variant exceeded expectations generated by previous surges. In the two to three weeks after the increase in Omicron cases, hospitalizations and deaths also increased, but more slowly and reached lower levels.

Still, as the Americans have learned from hard experience, the Omicron variant is a highly capable killer. Just over 200,000 of the more than 1,030,000 COVID-19 deaths in the country are likely due to some version of the Omicron variant, which arrived here around Thanksgiving and became dominant in January.

And don’t forget, Perlman said: It’s keep killing about 400 people a day in the United States.

It is not known how much of Omicron’s supposed mildness should be attributed to the protective effect of vaccines.

In June, the US Centers for Disease Control and Prevention. completed that COVID-associated hospitalizations among unvaccinated adults were 4.6 times higher than among vaccinated people. But the picture is murkier than such data would suggest.

Americans’ immune profiles run the gamut, making it difficult to place people into clear categories and compare how they fare when infected with different variants. Those who have been vaccinated are experiencing various degrees of decreased immunity, even with boosters. The same goes for people who have recovered from infections. The readiness of their immune systems depends on how long ago they had the infections, which variant infected them, their vaccination status, and other factors, such as their age and the medications they take.

With so many variables to consider, it’s difficult for researchers to draw a clear comparison between Omicron and its predecessors. But they have tried.

In one to study published in Nature, the scientists showed that Omicron was attracted to a wide range of human tissues. When observed in Petri dishes, the variant established itself in cells that mimicked the upper airways of the respiratory system, albeit less enthusiastically than the Delta variant. Furthermore, Omicron was far less adept at infecting lower respiratory tract cells, including lung tissue, than Delta or the original SARS-CoV-2 strain from Wuhan.

And in animal studies like hamsters other transgenic mice, the Omicron variant caused less weight loss (an indicator of severe disease) and caused less inflammation in the lungs than Delta or the parent strain.

Adding to the uncertainty is the fact that coronavirus testing was undergoing radical changes just as the Omicron variant took hold. As home testing has increased and fewer new infections have been reported to public health agencies, the ratio of cases on the one hand to hospitalizations and deaths on the other, a previously reliable measure of one’s ability to get sick variant, it became less reliable.

The staggering infectivity of the Omicron variant and its propensity to spawn new sub-variants further complicate the picture. At a recent meeting called by the Food and Drug Administration, even the agency’s experts shrugged when asked to compare subvariants.

Collectively, those Omicron subvariants pushed Delta out of the way so quickly that doctors and researchers didn’t have time to assemble groups of similar patients, genetically sequence the viruses that infected them, and compare how their illnesses proceeded.

That’s the kind of study that could shed light on the divergent experiences of Cathy Baron and Sara Alicia Costa. They are apparently well-matched examples of healthy women in their 40s, but Omicron attacked one of them like a lion and treated the other like a lamb. With the experiences of hundreds or thousands of people included, such research could reveal factors that push an Omicron infection in one direction or another.

There is a more direct way to tell how Omicron compares to earlier variants in its ability to sicken and kill: Researchers could deliberately infect volunteers with different versions of the coronavirus and track their physiological responses throughout their illnesses.

Chiu and colleagues at Imperial College London have such a task in mind and are planning “human challenge” studies involving Delta and Omicron variants to reflect one already done with the original version of the virus.

The resulting data could shed a clearer picture of exactly how Omicron behaves in healthy humans and how previous infection or different levels of vaccination affect an individual’s illness.

Chiu said a new study would seek to enroll people who gained immunity through vaccinations, past infections, or a combination of the two. That would give more insight into whether so-called hybrid immunity is a major bulwark against disease in the Omicron era.

If research confirms that the Omicron variant is in fact milder than its predecessors, and that getting it confers some protection against future illness, some may conclude that it’s time to let the virus spread.

Baron would take a while to convince himself of that.

“When people say, ‘Let’s just let it break’ and allow ourselves to get infected over and over again, that scares me,” he said. “I don’t want to just let it break. I don’t want to have it again.”

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