Omicron cases hit records, but here’s the silver lining
A slew of new studies have confirmed the silver lining of the omicron variant: Even though the number of cases is reaching record highs, the number of severe cases and hospitalizations has not increased. The data, some scientists say, points to a less worrying new chapter in the pandemic.
“We are now in a totally different phase,” said Monica Gandhi, an immunologist at the University of California at San Francisco. “The virus will always be with us, but I hope this variant causes so much immunity that it quells the pandemic.”
The omicron variant was discovered in South Africa just over a month ago, and experts warn there is still plenty of time for the situation to change. But data from last week suggests that a combination of widespread immunity and numerous mutations resulted in a virus that causes much less severe disease than previous iterations.
A study in South Africa found that patients admitted to hospital during the fourth wave of the omicron-dominated virus were 73% less likely to have severe disease than patients admitted in the third wave dominated by deltas . “The data is pretty strong now that hospitalizations and cases are decoupled,” said Wendy Burgers, an immunologist at the University of Cape Town.
At first, much of the alarm raised by the omicron was due to the variant’s large number of mutations, many of which are on the spike protein, the part of the virus responsible for helping it invade host cells. . These mutations, according to early data, allowed the virus to easily infect not only unvaccinated people, but also evade antibody responses from previous infections and vaccines. But the question remained as to how omicron would fare once it broke through 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 the factors is the ability of the virus to infect the lungs. Covid infections usually start in the nose and spread to the throat. A mild infection doesn’t travel much further than the upper respiratory tract, but if the virus reaches the lungs, it’s usually when more severe symptoms appear.
But five separate studies over the past week have suggested that the variant doesn’t infect the lungs as easily as previous variants. In a study, published as a preprint online by a large consortium of Japanese and American scientists, hamsters and mice infected with omicron suffered significantly less lung damage and were less likely to die than those infected with of the previous variants. Another study in Belgium found similar results in Syrian hamsters, which are known to suffer from particularly severe illness during previous iterations of the virus.
In Hong Kong, scientists studied a small number of patient lung tissue samples taken during surgery and found that omicron grew more slowly in those samples than other variants.
Burgers said this change in virulence was likely related to the evolution of the virus’s anatomy.
“Previously, it used two different pathways to get into cells, and now, due to all the changes to the spike protein, it prefers one of those pathways,” she said. “It seems to prefer infecting the upper respiratory tract rather than the lungs.”
That, Burgers said, could mean less serious infection, but also more transmissibility as the virus replicates more often in the upper respiratory tract, from where it can spread more easily.
While omicron may be effective in evading antibody attack, recent studies have also shown that it is much less successful in avoiding the second-line defenses of vaccines and previous infections: T cells and B cells.
T cells are responsible for attacking a virus once it enters the body’s cells if 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 preserved compared to previous strains of the virus. This means that for those who are vaccinated or have had a Covid infection in the past 6 months, their T cells are likely to be able to recognize the omicron and fight it off relatively quickly.
This latter research will need to be followed by a more in-depth study. If it stands up to closer examination, that could explain why current infections appear to be milder than in previous waves of the virus.
“When you start to see different types of data all pointing in the same direction, you start to be more confident that it’s going to hold up,” said Jessica Justman, epidemiologist at Columbia University Medical Center.
That said, as cases skyrocket, the absolute number of hospitalizations and deaths will always increase with them, even if those numbers increase more slowly.
“When your denominator is really big because a lot, a lot of people are infected, you always end up having a lot of people who need hospital care,” Justman said. A higher number of cases will also create disruption in work, travel and schooling.
Gandhi, of the University of California, San Francisco, said that while the number of cases could reach record highs, she hopes the combination of high transmissibility omicron and mild infection could signal the onset of the end. She pointed to another study done last week in Hong Kong, which showed that vaccinated patients infected with omicron also generated strong immune responses against other versions of the virus. That, she said, could explain why the number of cases quickly peaked in South Africa.
“I hope this variant will create a deep immunity in the population,” she said. “This will hopefully end the pandemic.”
(Except for the title, this story was not edited by NDTV staff and is posted from a syndicated feed.)