Prolonged Covid symptoms less likely to occur after omicron infection, study suggests

the omicron variant of Covid-19 seems less likely than delta to lead to long covidaccording to British researchers.

But because omicron is so much more contagious than previous variants, the sheer number of people who have been infected since it began spreading in the winter means there will still be many struggling with long-lasting symptoms, such as brain fogheadaches and debilitating fatigue.

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The new research, which was published Thursday in the lancetis an observational analysis of people who signed up for a smartphone app-led project called the ZOE Covid Study. Users regularly report any Covid symptoms, vaccination status, and other demographic information.

Since the app’s launch in March 2020, approximately 4.7 million people have registered, the majority of whom reside in the UK.

“For each successive wave of viruses, we’ve been looking at whether the likelihood of Covid lasting for a long time is affected by different variants,” said Claire Steves, an author of the new study and a senior clinical professor at King’s College London.

Steves and his team found no difference in the long-term prevalence of covid when they compared the original strain of the virus with later variants up to delta.

“We were very excited when omicron came along, especially since it went through our population very, very quickly,” Steves said. “We wanted to find out as quickly as possible what this meant for long-term covid.”

The researchers focused on data from 41,361 adults who tested positive for COVID-19 between June 2021 and the end of November 2021, when the delta variant was dominant, comparing them to 56,003 adults who tested positive after omicron was established between December 2021 and March 2022, when more than 70% of UK cases were estimated to be omicron.

The UK team defines Long Covid as having new or continuing symptoms at least one month after initial infection.

Nearly 11% of people who became infected during the delta period met the criteria. When the researchers looked at people infected during the omicron wave, the percentage of long-Covid patients fell to 4.5%.

All participants had been vaccinated prior to their infection. Some research has suggested that vaccines may offer little protection against the long Covid.

When Steves and his team took vaccination status into account, they continued to see a reduction in long-term risk of Covid during the wave of omicrons. “That’s a solid finding,” Steves said.

However, the research does not provide details on how long people experienced prolonged Covid or the severity of symptoms.

“This is an important piece of information,” said Andrea Lerner, a medical officer at the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health. She is affiliated with a major Long Covid study called RECOVERwhose goal is to hire at least 18,000 people.

“But what it doesn’t tell us is the clinical details about what they experience or how long they experience symptoms or effects,” Lerner said.

Increase in cases of prolonged covid

There is no definitive data on how many people can have Covid for a long time. Estimates are generally set to a range of 20% to 30% of all Covid infections.

Even if omicron is less likely to cause lasting symptoms, particularly in people who have been vaccinated, the actual number of people affected by prolonged covid isn’t going down, Steves said.

“In fact, it’s going up,” he said.

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Because the UK report tracked infections when the omicron BA.1 version was dominant, it is not yet clear whether the newer sub-variants BA.2.12.1 and BA.4 and BA.5that are taking hold in the US, will lead to more or less prolonged Covid symptoms.

Clinics specialized in long Covid in the US, which is currently averaging more than 100,000 cases per day, according to NBC News datathey are seeing many new patients who have recovered from omicron and are still experiencing a variety of symptoms.

“We’ve seen patients who got infected in December, January and February in our clinic,” said Dr. Upinder Singh, a professor of infectious diseases and chief of the division of infectious diseases at Stanford Medicine in California.

But while the ZOE app can collect user-driven data in real time, the backlog of long-term covid appointments makes it difficult for doctors treating long-term covid to know whether patients were infected during delta or omicron waves. .

“I don’t have the numbers to know if it’s more or less than after the delta, to be honest,” Singh said. “We’re scheduling so far away.”

Dr. Greg Vanichkachorn, an occupational medicine specialist at the Mayo Clinic in Rochester, Minn., said his team is also caring for long-time Covid patients who were infected during the wave of omicron.

“While the omicron variant may have a lower risk of long-term Covid, the large number of people with omicron means there may be a rapid increase in long-term Covid cases around the world,” Vanichkachorn said.

“Long-term covid remains a public health issue that needs to be addressed,” he said.

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