Mild omicron infections could finally quell the pandemic

A series of new studies confirmed the positive side of the omicron variant: Even as the number of cases rises to record highs, the number of severe cases and hospitalizations remains unchanged. The data, according to some scientists, would point to a new and less worrisome chapter in the pandemic.

“Now we are in a totally different phase“, He 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 finally quell the pandemic.”.

The omicron variant was discovered in South Africa just over a month ago, and experts warn that there is still plenty of time for the situation to change. However, data from last week suggests that a combination of widespread immunity and numerous mutations has resulted in a virus that causes much less severe disease than previous variants.

A study conducted in South Africa found that patients admitted to hospital there during the fourth wave of the omicron-dominated virus were 73% less likely to develop severe disease than those admitted during the third wave dominated by the delta variant.

“The data is pretty robust now that hospitalizations and cases are decoupled”Said Wendy Burgers, an immunologist at the University of Cape Town.

At first, much of the alarm about omicron was due to the large number of mutations in the variant, many of which are in the spike protein, the part of the virus responsible for helping it invade host cells.

Those mutations, early data suggested, allowed the virus to easily infect not only unvaccinated people, but also evade antibody responses from previous infections and vaccines. But the question remained how omicron would fare once he got past 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 of them is the ability of the virus to infect the lungs. COVID infections usually start in the nose and spread down the throat. A mild infection does not reach much beyond the upper respiratory tract, but if the virus reaches the lungs, this is usually when the most severe symptoms occur.

But five separate studies from last week suggested that the variant does not infect the lungs as easily as previous variants. In one study, published as a preprint online by a large consortium of Japanese and American scientists, hamsters and mice infected with omicron experienced much less lung damage and were less likely to die than those infected with earlier variants.

Another study in Belgium found similar results in Syrian hamsters, which are known to have experienced particularly severe illness with earlier versions of the virus.

In Hong Kong, scientists studied a small number of lung tissue samples from patients and found that omicron grew more slowly in those samples than other variants.

Burgers said this change in virulence likely had to do with how the anatomy of the virus changed.

“He used to use two different pathways to get into cells and now because of all the changes in the spike protein, he prefers only one“, he pointed. “It seems that it prefers to infect the upper respiratory tract rather than the lungs.”

This, Burgers said, could mean a less serious infection, but also more transmissibility, as the virus replicates more frequently in the upper respiratory tract, from where it can spread more easily.

While the omicron variant may be good at evading antibody attacks, recent studies have also shown that it is much less successful at avoiding the second-line defenses of vaccines and previous infections: T cells and B cells.

T cells are responsible for attacking the virus once it enters the cells of the body, in case the antibodies fail to prevent infection in the first place.

In a recent study by Burgers and colleagues, scientists used white blood cells from COVID patients to show that around 70-80% of the T-cell response is conserved compared to earlier strains of the virus. That means for those who are vaccinated or have had a COVID infection in the past 6 months, their T cells are likely to recognize the omicron variant and fight it off relatively quickly.

This last investigation will have to be followed with more studies. If it stands up to additional scrutiny, it could explain why current infections appear to be milder than previous waves of the virus.

Gandhi, from the University of California, San Francisco, said that while the number of cases could be reaching record numbers, he hopes that the combination of the highly transmissible omicron variant with a milder infection is a sign of the beginning of the end.

Gandhi mentioned another study conducted last week in Hong Kong, which showed that vaccinated patients infected with omicron also elicited strong immune responses against other versions of the virus. This, he said, could explain why the number of cases peaked quickly in South Africa.

“I hope that this variant creates a deep immunity in the population ”, Indian. “Hopefully, the pandemic will end.”