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Omicron less likely to cause long Covid than Delta variant: Lancet study

Long Covid is defined as having new or ongoing symptoms four weeks or more after the start of the disease, according to researchers.

June 21, 2022 / 12:40 PM IST
Image Source: Reuters

Image Source: Reuters

The Omicron variant of the SARS-CoV-2 virus is less likely to cause long Covid than the Delta strain, according to a study published in The Lancet journal.

Long Covid is defined as having new or ongoing symptoms four weeks or more after the start of the disease, the researchers said.

Symptoms include fatigue, shortness of breath, loss of concentration, and joint pain, which can adversely affect day-to-day activities, and in some cases can be severely limiting, they said.

The researchers found that the odds of experiencing long Covid were between 20-50 per cent less during the Omicron period versus the Delta period, depending on age and time since vaccination.

"The Omicron variant appears substantially less likely to cause long Covid than previous variants but still 1 in 23 people who catch COVID-19 go on to have symptoms for more than four weeks," said study lead author Claire Steves from King's College London, UK.

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COVID-19 Vaccine

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How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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The study identified 56,003 UK adult cases first testing positive between December 20, 2021, and March 9, 2022, when Omicron was the dominant strain. Researchers compared these cases to 41,361 cases first testing positive between June 1, 2021, and November 27, 2021, when the Delta variant was dominant.

The analysis shows 4.4 per cent of Omicron cases were long Covid, compared to 10.8 per cent of Delta cases. However, the absolute number of people experiencing long Covid was in fact higher in the Omicron period, the researchers said. This was because of the vast number of people infected with Omicron from December 2021 to February 2022, they said.

The UK Office of National Statistics estimated the number of people with long Covid actually increased from 1.3 million in January 2022 to 2 million as of May 1, 2022. "Given the numbers of people affected it is important that we continue to support them at work, at home and within the NHS," Steves added.
PTI
first published: Jun 21, 2022 12:40 pm
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