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Omicron Variant Appears to Be Less Likely to Cause Long COVID Than Delta

About double the percentage of patients infected with the Delta variant of COVID-19 reported long COVID symptoms compared to the Omicron variant, according to a UK study. That suggests that the newer variants, while much more contagious and widespread, might be less likely to cause lasting symptoms. On the other hand, the absolute number of patients with long COVID after Omicron is higher because of that crush of cases. Here is more information.

LONDON – With COVID-19 affecting such a high percentage of the population in the United States and elsewhere, one of the greatest concerns is that those patients will end up with long-term symptoms.

A new study suggests the situation might not be as serious as it seems. In a letter published in The Lancet, UK researchers from King’s College London advise that the Omicron variant is less likely to cause long COVID than the Delta variant.

"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 lead author Claire Steves, PhD, from King’s College London.

Those findings resulted from data derived from the ZOE COVID Symptom study app. It is the first peer-reviewed study to report on long COVID risk and the Omicron variant, according to the authors.

Patients are considered to have long COVID if they suffer new or ongoing symptoms four weeks or more after the start of the disease. Those symptoms might be fatigue, shortness of breath, loss of concentration and joint pain. In some cases, the symptoms can be severely limiting, the report notes.

The odds of experiencing long COVID were estimated to be between 20-50% less during the Omicron period vs. the Delta period, depending on age and time since vaccination.

For the study, researchers identified 56,003 UK adults first testing positive between Dec 20, 2021, and March 9, 2022, who satisfied the inclusion criteria. Those participants, designated as omicron patients, were compared to 41,361 UK adult cases first testing positive between June 1, 2021, and Nov 27, 2021, referred to as delta cases.

“In both periods, female participation was higher than male participation (55% for omicron and 59% for delta cases). Delta and omicron cases had similar age (mean age 53 years) and prevalence of comorbidities (around 19%),” the authors point out.

Results indicate that, among omicron cases, 2,501 (4·5%) of 56,003 people experienced long COVID and, among delta cases, 4,469 (10·8%) of 41,361 people experienced long COVID. “Omicron cases were less likely to experience long COVID for all vaccine timings, with an odds ratio ranging from 0·24 (0·20–0·32) to 0·50 (0·43–0·59). These results were also confirmed when the analysis was stratified by age group,” the authors note.

The absolute number of patients experiencing long COVID actually was higher in the Omicron period, however, because of the large number of people infected with Omicron from December 2021 to February 2022, according to the report.