Long COVID risk lower with Omicron than Delta, study finds

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New research has compared the risk of getting long COVID from two different SARS-CoV-2 variants, the virus that causes COVID-19.
Researchers from King’s College London recently found that people with Omicron infections are 20-50% less likely to develop long COVID symptoms than those who had the Delta variant.
The research team also found the absolute number of people with long COVID symptoms was higher when the Omicron variant was dominant compared to Delta, because of the more contagious nature of Omicron.

It has been a little over two years since the World Health Organization (WHO) declared COVID-19 a pandemic in March 2020. As of June 20, 2022, more than 6.3 million people have died globally from the contagious disease and almost 536 million people around the world have had COVID-19.

As the pandemic continues, researchers are slowly learning more about COVID-19 symptoms, including those that linger within the body, now known as long COVID.

Symptoms of long COVID include fatigue, loss of smell, hearing loss, muscle pain, brain fog, and memory loss. Recent research has shown that some patients experienced impaired memory and loss of concentration for at least half a year.

A new study from King’s College London found that people who experienced SARS-CoV-2 infections with the Omicron variant were less likely to have long COVID symptoms compared to those who had the Delta variant.

The study was recently published in the journal The Lancet.

Delta vs. Omicron

SARS-CoV-2 has mutated and changed throughout the pandemic. As a result, many variants have emerged.

The initial SARS-CoV-2 variant was Alpha, followed by the Beta, and Gamma variants.

In April 2021, the Delta variant became the main variant of the pandemic. Because of Delta’s aggressive nature, researchers found it to be 40-60% more transmissible than the Alpha variant.

Currently, the most common SARS-CoV-2 variant is Omicron. Researchers have found that Omicron spreads easier but tends to cause less severe symptoms than previous variants.

Reduced long COVID symptoms

In regards to this new study, Dr. Claire Steves, reader at King’s College London and lead author of this study, said they wanted to know whether the risk of getting long COVID was the same or different for the Omicron variant compared to Delta.

“We had already seen that for Delta and Alpha the risk was not detectably different from the original strain, so we wanted to see if this was still the case with Omicron,” she told Medical News Today.

Dr. Steves said this was of particular interest because of three reasons:

With such a large number of people affected by Omicron, any difference would have a big impact on the numbers of people affected.
Researchers found that early in the onset of the disease, the severity of symptoms was less and more people were asymptomatic.
They also observed less anosmia—a loss of smell—in Omicron infections, which has been very commonly reported as a symptom of long COVID.

For their research, Dr. Steves and her team analyzed data from about 56,000 adult coronavirus cases in the United Kingdom. The infections took place between December 2021 and March 2022 when Omicron was the dominant strain.

Researchers then compared these cases to over 41,000 COVID-19 cases between June and November 2021 when Delta was the dominant strain.

The researchers found that 4.4% of Omicron cases experienced long COVID symptoms, compared to 10.8% of Delta variant cases. They deduced that a person’s odds of contracting long COVID symptoms were 20-50% less during the time when Omicron was dominant compared to when Delta was the presiding variant.

“We expected this to be the case because we know that a major risk factor for long COVID is the severity of early disease — both for people who are hospitalized and also even in the community where the number of symptoms in the first week related to the risk of long COVID in our early work,” Dr. Steves explained.

“In addition, Omicron seems to attack the deep lung tissue less than Delta, so this may be a factor. That is, there is less lung scarring in Omicron,” she added.

However, Dr. Steves and her team did observe the absolute number of people with long COVID symptoms was higher during the Omicron period. They attribute that finding to the larger number of people with Omicron infections due to its high contagion rate.

Different types of long COVID?

According to Dr. Steves, her team’s next steps for this research include looking at the way COVID-19 symptoms evolve over time and whether they can use symptoms and their evolution to identify sub-forms of long COVID.

“We will also be looking at whether these (also) change in relation to the variants,” she said.

MNT also spoke with Dr. Jimmy Johannes, pulmonologist and critical care medicine specialist at MemorialCare Long Beach Medical Center in Long Beach, CA, about this research.

Dr. Johannes said he was encouraged that patients who experienced COVID-19 with the more prevalent Omicron variant had less incidence of long COVID.

“The Delta variant seems to be more virulent compared to the Omicron variant, and has higher rates of severe illness, worse symptoms, and hospitalizations compared to the Omicron variant,” he explained.

“Given that the case definition of long COVID is just a duration of symptoms for weeks, it could be that if you had less a severe disease, people might get better faster on average,” he said.

For the next steps in research into long COVID, Dr. Johannes would like to see the distribution of symptoms between the Delta and Omicron patient populations.

“That would help us figure out if there is a difference in the syndromes that we see between the two variants,” he added.

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