Omicron infections appear to be milder, according to three research teams


Three separate teams of scientists on two continents have found that Omicron infections more often lead to mild illness than earlier variants of the coronavirus, giving hope that the current outbreak may not be as catastrophic as feared despite the skyrocketing the number of cases.

Researchers examined Omicron’s journey through populations in South Africa, Scotland and England. The results in each setting, while still preliminary, all suggest that the variant was less likely to send people to hospitals.

“Since it’s everywhere and given that it’s going to be so transmissible, anything that reduces gravity will be better,” said Natalie Dean, a biostatistician at Emory University in Atlanta.

Since the discovery of the Omicron variant in southern Africa in November, scientists have struggled to know if it causes more severe disease compared to other variants – and if so, in whom.

The new research suggests that the variant may have some biological characteristics that make it a little less dangerous than Delta, the variant that has dominated the world from the summer until now.

But Omicron’s reduced risk of hospitalization in all three countries also appears to be largely due to the immunity of these populations. Many of those infected were already protected against serious illness, either from previous infections or from vaccinations.

While the new research is encouraging, experts warn that the wave arriving in many countries may still flood hospitals with Omicron cases, simply because the variant spreads much more easily than previous versions of the coronavirus.

“I don’t mean to be alarmist, but I don’t think you can let your guard down,” said Christina Ramirez, a biostatistician at the University of California, Los Angeles.

Americans should take rapid tests before holiday events and should congregate outside, open windows or find other ways to improve ventilation, Dr Ramirez said.

While Omicron can cause milder illness on average, it also spreads faster than any variant to date. It is now the dominant variant in the United States, Europe, and many other parts of the world.

Still, encouraging news arrived from South Africa on Wednesday, suggesting that these outbreaks may not last as long as previous ones. Omicron has fueled a record number of new daily cases, but officials reported on Wednesday that the wave of infections may have peaked.

As infections in the United States have averaged 154,000 daily cases over the past week, federal health officials have added a defense against the growing threat to hospitals. The Food and Drug Administration on Wednesday cleared the first pill to treat Covid-19, offering highly effective treatment for serious illnesses.

The drug, developed by Pfizer and known as Paxlovid, is approved for Covid patients 12 years of age and older who are at risk of becoming seriously ill. Pfizer has reported that its pills may work against the Omicron variant.

The three studies from the UK and South Africa confirm that Americans will benefit from some protection against serious illnesses through vaccinations and booster shots. More than 200 million Americans, or more than 60% of the population, are now fully immunized.

But the United States lags behind other countries, some of which have vaccinated more than 80 percent of their population. And only 63 million Americans have received reminders, which offer the best protection against serious illnesses and infections caused by Omicron.

The South African study focused on the upsurge in Omicron cases since November. The risk of hospitalization was about 70% lower in people infected with Omicron, compared to those infected with other variants of the coronavirus, the researchers found.

The authors speculated that the milder cases could be due in part to the fact that Omicron was more successful at re-infecting people who had previously had Covid-19. While the variant may escape antibodies from previous infections and become established in the body, it may not be able to evade the powerful but slower immune responses that prevent serious illness.

In South Africa, researchers estimate that around 70% of people had Covid infections before the Omicron wave. About 30 percent have been vaccinated. The authors were unable to separate the protection provided by infections from that resulting from vaccinations.

They also warned that their data was collected at the start of the Omicron wave, when the overall infection rate was quite low. Those infected with relatively mild symptoms might have been more likely to be admitted to hospitals at the time, before wards filled up.

In Scotland, researchers looked at the Delta and Omicron cases in November and December, looking at how many patients with each variant were admitted to a hospital. Omicron infections are associated with a two-thirds reduction in the risk of hospitalization compared to the Delta variant, the researchers found.

Mark Woolhouse, professor of infectious diseases at the University of Edinburgh and co-author of the new study, said Omicron’s surge meant that even if these preliminary results held up, the variant would still put a lot of people in in hospitals very quickly.

Also on Wednesday, a team of researchers from Imperial College London compared the cases of Omicron and Delta in the first two weeks of December and reported a reduction in hospital visits, albeit a smaller reduction. to that observed by their Scottish colleagues.

Early estimates suggest that compared to cases of the Delta variant, people infected with Omicron are on average 15-20% less likely to present in hospitals overall and 40-45% less likely to be hospitalized for a period of time. night or more.

The team was able to distinguish the results of infection with Omicron on people who had been vaccinated, previously infected or lacked any immunity. They confirmed the South African researchers’ suggestion that acquired immunity helped moderate Omicron infections on average.

The difference between the results of the English and Scottish studies may also be partly due to differences in what was measured. The team at Imperial College London included people who had just visited a hospital, in addition to those who had to be bedridden for more serious illness. Scottish researchers only looked at hospital admissions.

The two teams of scientists have warned that their results are still preliminary. On the one hand, Omicron continues to make its way through Britain and has yet to make much headway among the elderly who may be at higher risk of hospitalization.

And even though the individual cases are mild, Omicron still poses a serious risk to hospitals because cases are exploding so quickly. “We’re not in a place to treat this like a cold,” said Azra Ghani, co-author of the Imperial College London study.

William Hanage, an epidemiologist at Harvard TH Chan School of Public Health, said the new findings made it clear that people who had not been vaccinated and had not yet had Covid were particularly at risk.

Because Omicron is spreading rapidly, there is a good chance that they will be infected in the coming months, he said. If this is the case, they will have no immunity to lessen the severity of the infection.

“If you’re not vaccinated and you’ve never been infected, it’s a little less serious than Delta,” Dr Hanage said. “But it’s kind of like saying you get hit on the head with a hammer instead of two.” And the hammers are more likely to hit you now.

While the past few weeks have brought a flood of new data on Omicron, there are still many questions about how the weeks to come and how hospitalization rates will increase.

Chris Robertson, an epidemiologist at the University of Strathclyde and co-author of the Scottish study, warned that the holiday season would slow down the collection of data he and others would need to update their findings.

“Normally I would do this scan every week, but now it will be two to three weeks before there are any further updates on this,” he said.

Nicholas Reich, biostatistician and infectious disease modeler at the University of Massachusetts at Amherst, said, “We have to be prepared to wait for answers and be prepared to swim in a bit of uncertainty. “

But a team of modelers leading a project called the Covid-19 Scenario Modeling Hub released a statement on Wednesday that made it clear that even if they adjusted their projections, the writing was already on the wall.

“The best information currently available to us indicates that the threat posed by Omicron is substantial and imminent, and individuals and governments must be prepared to respond accordingly,” they warned.


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