A spate of new studies on lab animals and human tissues are providing a possible explanation of why the omicron variant causes milder disease than previous versions of the coronavirus.
In studies on mice and hamsters, omicron produced less-damaging infections, often limited largely to the upper airway: the nose, throat, and windpipe. The variant did much less harm to the lungs, where previous variants would often cause scarring and serious breathing difficulty.
In November, when the first report on the omicron variant came out of South Africa, scientists could only guess at how it might behave differently from earlier forms of the virus. All they knew was that it had a distinctive and alarming combination of more than 50 genetic mutations.
Previous research had shown that some of these mutations enabled coronaviruses to grab onto cells more tightly. Others allowed the virus to evade antibodies, which serve as an early line of defense against infection. But how the new variant might behave inside of the body was a mystery.
“You can’t predict the behavior of virus from just the mutations,” said Ravindra Gupta, a virus expert at the University of Cambridge.
Over the past month, more than a dozen research groups, including Gupta’s, have been observing the new pathogen in the lab, infecting cells in petri dishes with omicron and spraying the virus into the noses of animals.
As they worked, omicron surged across the planet, readily infecting even people who were vaccinated or had recovered from infections.
But as cases skyrocketed, hospitalizations increased only modestly. Early studies of patients suggested that omicron was less likely to cause severe illness than other variants, especially in vaccinated people. Still, those findings came with a lot of caveats.
For one thing, the bulk of early omicron infections were in young people, who are less likely to get seriously ill with all versions of the virus. And many of those early cases were happening in people with some immunity from previous infections or vaccines. It was unclear whether omicron would also prove less severe in an unvaccinated older person, for example.
Experiments on animals can help clear up these ambiguities, because scientists can test omicron on identical animals living in identical conditions. More than a half-dozen experiments made public in recent days all pointed to the same conclusion: Omicron is milder than delta and other earlier versions of the virus.
On Wednesday, a large consortium of Japanese and American scientists released a report on hamsters and mice that had been infected with either omicron or one of several earlier variants. Those infected with omicron had less lung damage, lost less weight, and were less likely to die, the study found.
Although the animals infected with omicron on average experienced much milder symptoms, the scientists were particularly struck by the results in Syrian hamsters, a species known to get severely ill with all previous versions of the virus.
(New York Times)
In British studies, good news on Omicron
LONDON — People who contracted the Omicron variant of the coronavirus were about half as likely to need hospital care as those infected with the Delta variant, and one-third as likely to need emergency care, according to a report issued on Friday by British health officials.
The analysis of public data also found that vaccination offers strong protection against hospitalization and severe illness following Omicron infection, helping prevent the worst outcomes even as infection rates in Britain soar to record levels.
The findings represent some of the largest sets of real-world data to be released since the highly contagious variant was first discovered in late November, and adds to a growing body of evidence that Omicron may not present as great a danger of hospitalization and severe illness to the public as earlier variants.
“The latest set of analysis is in keeping with the encouraging signs we have already seen,” said Susan Hopkins, the chief medical adviser at the health security agency.
The risk of being admitted to a hospital for Omicron cases was 65 percent lower for those who had received two doses of a vaccine, compared with those who had not received any vaccination.
The rate of hospitalization was even lower among those who had received three doses of vaccine, according to the report, which was issued by the U.K. Health Security Agency. People who had received booster doses were 81 percent less likely to be admitted to the hospital, compared with unvaccinated people, according to the agency.
The agency analyzed 528,176 Omicron cases and 573,012 Delta cases between Nov. 22 and Dec. 26 to assess the risk of hospitalization in England. The researchers included all cases diagnosed in the community and then assessed the risk of general admission to the hospital or admission through emergency care.
In a second study, the agency examined just symptomatic cases, linked with hospitalization data, and found that three doses of a vaccine reduced the risk of hospitalization for people with the Omicron variant by 88 percent, compared with unvaccinated people with that variant.
While the results were encouraging, the agency said it would take more time to assess the severity of Omicron infections after admission to the hospital.
The South African government said Thursday that data from its health department suggested that the country had passed its Omicron peak without a major spike in deaths, offering cautious hope to other countries grappling with the variant .(New York Times)
FDA approval sought for another vaccine
The American biotechnology company Novavax said on Friday that it would ask the Food and Drug Administration to authorize its Covid-19 vaccine in January.
If approved, the vaccine would be the fourth to become available in the United States, which already has ample supplies. Novavax said that it had sent the FDA the final data needed to complete its application for emergency use authorization.
Novavax, based in Maryland, won $1.6 billion in support from the United States government in 2020 to develop a vaccine made of proteins from the coronavirus, but it has lagged behind vaccine developers Pfizer-BioNTech and Moderna, and has struggled with its clinical trials and manufacturing.
Still, the company’s vaccine, known as Nuvaxovid, has recently received a cascade of positive news. Earlier in December, the company’s researchers published a report in The New England Journal of Medicine, presenting evidence that Nuvaxovid was 90 percent effective against symptomatic infections and 100 percent effective in averting moderate to severe disease.
The World Health Organization granted Nuvaxovid an emergency-use listing, and the European Commission authorized it as well. Nuvaxovid has side effects that are usually mild or moderate and that clear up within a couple days. Protein-based vaccines have been used for decades and generally have a strong safety record.
It is not yet clear, though, how well Nuvaxovid will work against the more contagious Omicron variant. In studies of other vaccines, researchers have found that Omicron is consistently better at evading vaccines. Novavax is developing an Omicron-specific version of its product and will soon test it, the company said. (New York Times)
Millions had variant in Britain
LONDON — New figures from Britain’s official statistics body estimate that about 1 in 25 people in private households in England had COVID-19 in the week before Christmas, as the highly transmissible omicron variant spread rapidly across the country.
The number jumped from 1 in 45 in the previous week, the Office for National Statistics said Friday.
One in 25 is the equivalent of about 2 million people with coronavirus in England, the highest number since the statistics body began estimating infection levels in May 2020.
The figure was even higher in London, the British capital, where officials said around 1 in 15 people was likely to test positivefor the coronavirus in the week to Dec. 23. (Associated Press)
Daily record for cases set in S.C.
COLUMBIA, S.C. — South Carolina’s health department reported Friday a record-high number of nearly 9,000 COVID-19 cases in one day.
The record-shattering 8,882 cases confirmed by the South Carolina Department of Health and Environmental Control comes less than a year after the state marked its previous high of 7,686 cases in early 2021.
“I think January’s going to be a very difficult month for South Carolina,” Department Director Dr. Edward Simmer said during a Friday news conference.
The state has seen significant rises in the number of people hospitalized and on ventilators in the past week. Hospitals are managing the increase, but the rise in cases has strained staff, Simmer said. Some emergency rooms and urgent cares are already getting overwhelmed, with wait times increasing, he added.
A third of the state’s hospitals reported critical staffing shortages to the US Department of Health and Human Services on Thursday. (Associated Press)