Omicron seen as milder coronavirus but scientists aren’t sure

For over two years, Cathy Baron and Sara Alicia Costa managed to dodge the coronavirus. But despite being fully vaccinated and boosted, they were eventually caught by the Omicron variant.

Baron is an actress and dance teacher based in Santa Monica. Costa is an architect based in Austin, Texas. Both are 40 and healthy. But the two friends saw two very different sides of the variant, which they expected to be gentler on their victims than previous tribes.

For Costa, the Omicron variant lived up to its reputation for mildness, causing a headache and “something like a bad cold” for a few days. A week after testing positive, she visited Baron and surfed in Santa Monica.

Baron’s illness was deeply chagrining. She was exhausted for several days with a high fever and debilitating muscle pain and was too exhausted to teach her pole dance class for three weeks. Two months later, she’s still struggling with fatigue, brain fog, and episodic coughing fits. She hopes never to repeat this experience.

Baron and Costa are what scientists would dismiss as “n of 2”. If their experience were a study, the sample size would be far too small to draw any conclusions, particularly ones as important as whether the Omicron variant is really less virulent than the SARS-CoV-2 variants that came before it came.

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

“That’s an excellent question,” said Dr. Stanley Perlman, a University of Iowa virologist and a leading expert on coronavirus. Many researchers think they know the answer, and “I think it’s true” that the omicron variant causes milder diseases, he said. But the real picture is “not clear,” he warned.

Omicron came to the United States at a time when 60% of Americans had the protection of COVID-19 vaccines and about a third of Americans (including some vaccinates) had a prior infection. Not only was there a high level of population immunity, those who fell ill had access to treatments not available to people who fell ill with the original strain from Wuhan, China, or the Alpha and Delta variants that followed .

Perhaps these are the reasons that Omicron-infected people tended to have milder illnesses.

“It’s commonly said that Omicron is inherently less pathogenic, but there’s no real evidence for that,” said Dr. Christopher Chiu, a COVID-19 researcher at Imperial College London.

“Comparisons to Delta are like apples and oranges,” he said. “Delta was in circulation at a time when many were unvaccinated or already infected. In contrast, Omicron mostly causes breakthrough infections in people who already have partial protection from immunity from vaccines or infections.”

Since it first appeared in November, researchers have found that Omicron was less likely to send infected people to the hospital or their graves compared to previous variants.

First in South Africa and later in communities across America, the new variant defied expectations created by earlier fluctuations. In the two to three weeks after the rise in omicron cases, hospitalizations and deaths also rose – but more slowly, and they had peaked at lower levels.

As the Americans have learned through hard experience, the Omicron variant is still an extremely capable killer. A little over 200,000 of the country’s COVID-19 deaths are likely due to a version of the Omicron variant, which arrived here around Thanksgiving and became dominant in January.

And don’t forget, Perlman added, about 400 people still die every day in the United States.

How much of Omicron’s supposed mildness is due to the protective effects of vaccines isn’t really known.

In June, the Centers for Disease Control and Prevention concluded that COVID-related hospitalizations were 4.6 times higher among unvaccinated adults than vaccinated individuals. But the picture is murkier than such data suggests.

Americans’ immune profiles vary widely, making it difficult to neatly categorize people and compare how they fared when infected by different strains. Those who have been vaccinated experience varying degrees of declining immunity even when boosted. The same applies to people who have recovered from infections. The readiness of their immune system depends on how long ago they were infected, which variant infected them, their vaccination status and factors such as age and the medications they are taking.

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

In a study published in Nature, scientists showed that omicron was attracted to a variety of human tissues. When observed in petri dishes, the variant became established in cells that mimicked the upper airways of the respiratory system, albeit with less enthusiasm than the delta variant. Additionally, Omicron was far less adept at infecting lower respiratory tract cells, including lung tissue, than Delta or the original SARS-CoV-2 strain that left Wuhan.

And in studies infecting animals like hamsters and genetically engineered mice, the Omicron variant caused less weight loss (an indication of serious disease) and less inflammation in the lungs than either Delta or the original strain.

Adding to the uncertainty is the fact that coronavirus testing has undergone sweeping changes just as the Omicron variant has taken hold. As home testing expanded and fewer new infections were reported to health officials, the relationship between cases and hospitalizations and deaths – a previously reliable measure of a variant’s disease viability – became less reliable.

The Omicron variant’s amazing contagiousness and propensity to split off new subvariants further complicate the picture. At a recent meeting convened by the Food and Drug Administration, even experts from the agency shrugged when asked to compare the subvariants.

Collectively, these Omicron subvariants pushed Delta aside so quickly that doctors and researchers didn’t have time to gather groups of similar patients, genetically sequence the viruses that infected them, and compare how their diseases progressed.

This is the kind of study that could shed light on the different experiences of Cathy Baron and Sara Alicia Costa. They are a seemingly well-matched pair of healthy 40-year-old females, 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, such research could uncover factors that nudge Omicron infection one way or the other.

There’s a more direct way to learn how Omicron compares to previous variants in its ability to sicken and kill. Researchers could intentionally infect volunteers with different versions of the coronavirus and track their physiological responses to infection over the course of an illness.

Chiu and his colleagues from Imperial College London have such an undertaking in mind. They are planning “human challenge” studies with the Delta and Omicron variants to mirror a study already done with the original version of the virus.

The resulting data could provide a clearer picture of exactly how Omicron behaves in healthy people, and how previous infection or different vaccination levels affect a person’s disease.

Chiu said a new study would try to enroll people who gained immunity through vaccination, a previous infection, or a combination of both. That would give them more insight into whether so-called hybrid immunity is an important bulwark against getting sick in the Omicron era.

If research confirms that the Omicron variant is indeed milder than its predecessors, and that taking it offers some protection against future illnesses, some might conclude it’s time to let the virus spread.

Baron would let himself be persuaded.

“When people say, ‘Let’s have a blast,’ and we keep getting infected, it scares me,” she said. “I don’t want to just let it rip. I don’t want to get it again.”

https://www.latimes.com/science/story/2022-08-12/scientists-question-whether-omicron-is-really-less-dangerous-than-other-coronaviruses Omicron seen as milder coronavirus but scientists aren’t sure

Russell Falcon

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