Several new studies have confirmed the positive side of the Omicron version: Even that When the number of cases is entered in the record, The number of serious cases and hospitalizations is not there. data, some scientists say, A sign of a new and less worrying chapter in the pandemic.
“Now we’re in a completely different phase,” said Monica Gandhi, an immunologist at the University of California, San Francisco. “The virus will always be with us, but I hope this variant causes so much immunity that it will suppress the pandemic.”
The Omicron variant was discovered in South Africa only a month ago, and experts warn that the situation is still a long time to change. But last week’s figures show that The combination of widespread immunity and multiple mutations has resulted in a virus that causes much less severe disease than previous iterations.
A study in South Africa found that patients hospitalized during the fourth wave of the Omicron-dominated virus were 73 percent less likely to develop serious illness than patients admitted during the Delta-dominated third wave. “The data is very strong now that hospitalizations and cases are unreported,” said Wendy Berger, an immunologist at the University of Cape Town.
First, much of the alarm about Omicron was due to the large number of mutations in the type, many of which occur in the spike protein, the part of the virus responsible for helping it invade host cells. Those mutations, preliminary data suggested, allowed the virus not only to easily infect unvaccinated people, but also to evade earlier infections and antibody responses from vaccines. But the question remained how Omicron would perform after crossing those first lines of defense.
Several factors appear to have made the Omicron variant less virulent or severe than previous waves of COVID-19. One factor is the virus’s ability to infect the lungs. The COVID infection usually starts in the nose and spreads to the throat. A mild infection does not reach far beyond the upper respiratory tract, but if the virus does reach the lungs, it is usually when the most severe symptoms occur.
But five different studies from last week suggested that this type doesn’t infect the lungs as easily as the previous ones. In one study, published online as a preprint by a large consortium of Japanese and American scientists, hamsters and rats. Omicron experienced very little lung damage and was less likely to die than those infected with previous forms. Another study in Belgium found similar results in Syrian hamsters, which are known to experience particularly severe illness with previous iterations of the virus.
In Hong Kong, scientists studied a small number of lung tissue samples collected from patients who had surgery and found that omicrons grew more slowly in those samples than in other types.
Berger said this change in the virus likely had to do with how the virus’s anatomy changed.
“He used to use two different routes to get into cells and now, because of all the changes in the spike protein, he prefers one of those routes,” he said. “It seems to prefer to infect the upper respiratory tract rather than the lungs.”
This could mean a less severe infection, but also greater transmission potential, Berger said, as the virus replicates more frequently in the upper respiratory tract, from where it can spread more easily.
While Omicron may be good at warding off antibody attacks, recent studies have also shown that it is much less successful at evading the second line of defense against T cells and previous infections: T cells and B cells.
T cells are responsible for attacking the virus after it has entered the body’s cells if antibodies fail to stop the infection in the first place. In a recent study by Berger and colleagues, scientists used white blood cells from COVID patients to show that about 70–80% of the T-cell response is preserved compared to earlier strains of the virus. This means that people who have been vaccinated or who have had a COVID infection in the past 6 months, their T cells are likely to be able to recognize the micron and fight it relatively quickly.
This final investigation will have to be followed up with more study. If it stands up to additional scrutiny, it could explain why the current infection appears to be milder than previous waves of the virus.
“When you start looking at different types of data, all pointing in the same direction, you start to feel more confident that it will last,” said Jessica Justman, MD, an epidemiologist at Columbia University Medical Center.
That said, as cases skyrocket, the absolute numbers of hospitalizations and deaths will continue to rise with them, even if those numbers gradually increase.
“When your denominator is huge because many, many people are getting infected, there are still many people who go to the hospital and need care,” Justman said. The rising number of cases will also continue to cause disruption in work, travel and education.
Gandhi of the University of California, San Francisco said the number of cases could reach a record, Hopefully a combination of highly permeable omicrons and mild infections may signal the beginning of the end. He pointed to another study conducted in Hong Kong last week, which showed that vaccinated patients infected with Omicron also elicited stronger immune responses against other versions of the virus. This, he said, could explain why the number of cases in South Africa rose rapidly.
“I hope this variant creates deep immunity in the population,” he said. “Hopefully the pandemic will be over.”