The Omicron SARS-CoV-2 variant is as much as 50% less likely to cause long COVID than its predecessor Delta variant, according to a letter published yesterday in The Lancet.
But the authors of the study point out that, even though the rate of Omicron long COVID appears to be lower, because so many have been infected with the newer variant, the actual number of affected people is very high.
Though more easily transmitted, the Omicron variant causes less severe disease in general than Delta, numerous previous studies have shown.
Long COVID 24% to 50% lower with Omicron
Researchers from King's College London identified 56,003 UK adults who tested positive for COVID-19 from Dec 20, 2021, to Mar 9, 2022. Given that more than 70% of UK cases were attributable to Omicron during that stretch, they categorized them as Omicron patients. Likewise, 41,361 adults who tested positive from Jun 1, 2021, to Nov 27, 2021, were classified as Delta patients.
Women outnumbered men in both groups, 55% for Omicron and 59% for Delta. But people in both groups were of similar age (mean, 53 years) and had a similar rate of comorbidities (around 19%).
They defined long COVID as having new or ongoing symptoms 4 weeks or more after COVID-19 onset. Symptoms include fatigue, shortness of breath, loss of concentration, and joint pain. These symptoms can limit daily activities and in some cases be severely limiting.
Patients logged their symptoms via a smartphone app.
The investigators found that 2,501 (4.5%) of the Omicron patients and 4,469 (10.8%) of Delta patients experienced long COVID. Regardless of the timing of vaccine, the odds of long COVID for Omicron patients were 24% to 50% less than for Delta patients (95% confidence intervals, 20% to 32% and 43% to 59%, respectively).
Though lower rate, higher long COVID numbers
The authors write, "We believe this is the first peer-reviewed study to report on long COVID risk associated with infection by the omicron variant, highlighting that health surveillance using smartphone apps can produce rapid insights, which we have consistently shown are accurate and subsequently replicated."
But because Omicron leads to so many cases, they note, the absolute number of people experiencing long COVID was higher in the Omicron period. "Our data are consistent with the UK Office for National Statistics, who estimated that the numbers of people experiencing long COVID actually increased from 1.3 million in January, 2022, to 1.7 million in March, 2022," the authors add.
They conclude, "Considering the UK omicron peak of more than 350,000 new symptomatic COVID-19 cases per day estimated on March 26, 2022, by the ZOE app model and 4% of cases being long COVID, future numbers with long COVID will inevitably rise."
Senior author Claire Steves, PhD, said in a King's College London news release, "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. Given the numbers of people affected it's important that we continue to support them."
Other new long COVID studies
In other long-COVID news, a study of 173 recovered COVID-19 patients in the St. Joseph's Health Network in New Jersey reveals that 23.1% of patients still experienced at least one persistent symptom 2 years after infection. The findings appeared yesterday in Clinical Microbiology and Infection.
Participants completed a questionnaire in March and April 2021, before Delta had become dominant in the United States.
The most common reported long-COVID symptoms were shortness of breath (13.2% of people), fatigue (12.1%), difficulty focusing/brain fog (10.4%), memory loss (9.2%), and anxiety (8.1%).
In another new study, conducted over 15 months from February 2020 through May 2021 and published in The Journal of Neuropsychiatry, specialists with the Massachusetts General Hospital (MGH) detail 87 confirmed and 13 presumed cases of long COVID in patients who weren't hospitalized after contracting COVID-19.
A key feature of the study is that 75% of the patients were white educated women. Senior author Zeina Chemali, MD, MPH, director of the Neuropsychiatry Clinics and Training at MGH, said in a hospital news release, "Even though we know Black Americans and Latinx individuals got very sick with COVID-19, we did not see them in the long haulers clinic."
"Commonly, patients with long COVID present with 'brain fog,' a vague description including lack of sleep, anxiety, depression and a history of headache or migraine combined with trouble with attention and word finding difficulties as well as executive dysfunction," she added.
