Omicron Less Likely Than Early Variants to Cause Symptoms of Long COVID-19

Patients are less likely to have symptoms of long COVID-19 after contracting the Omicron (BA.1) variant of SARS-CoV-2 compared to an earlier, or wild-type, variant, according to a study conducted in Switzerland. Results of the prospective study will be presented at the April 15-18 European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Copenhagen.

“With the emergence of Omicron, its ongoing global dominance and the accompanying explosion of infections, it is vital to find out more about who is at risk of long COVID-19 and why,” said Carol Strahm, Division of Infectious Diseases and Hospital Epidemiology, Cantonal Hospital St Gallen, Switzerland, in a press release.

Strahm explained that most data about long COVID-19 are restricted to the pre-Omicron period of COVID-19. Treatment options are limited today, and some patients still suffer debilitating illness, Strahm noted.

The Swiss investigators conducted a prospective study to compare rates of long COVID-19 symptoms in health care workers diagnosed with wild-type SARS-CoV-2 virus, Omicron, or both. They also compared rates of long COVID-19 with a control group of uninfected patients.

Between June and September 2020, investigators recruited 1201 health care workers (81% female; median age 43) across 9 nationwide health care networks. Patients were asked to complete regular nasopharyngeal swabs and antibody tests for COVID-19, provide vaccination status, and fill out online questionnaires—March 2021 (Q1), September 2021 (Q2) and June 2022 (Q3)—about the status of their long COVID-19 symptoms, if applicable.

The questionnaire had a list of 18 long COVID-19 symptoms, including loss of sense of smell and/or taste, tiredness/weakness, burnout and exhaustion, hair loss, and it also asked participants to rank level of fatigue.

Compared to the control, health care workers with the wild-type virus had a 67% higher risk of experiencing long COVID-19 symptoms in Q1 and the risk of fatigue was 45% higher than the control. By Q3, the risk of long COVID-19 was reduced to 37% in patients with wild-type infection compared to the control. The risk of fatigue was not significantly worse in patients with wild-type virus.

Patients tested for the Omicron variant were no more likely to report symptoms of long COVID-19 compared to uninfected participants, nor were they more likely to have a higher rate of fatigue. Additionally, patients who originally had wild-type infection but were reinfected with Omicron did not have a worse risk of having long COVID-19 or fatigue compared to patients who only had wild-type infection.

Further, SARS-CoV-2 vaccination prior to Omicron infection did not reduce the risk of long COVID-19 in reinfected individuals (Omicron infection following previous infection of wild-type variant) compared to people infected with the wild-type variant.

The study is limited to a mostly healthy, young, vaccinated population of women, which may limit the generalizability to people who are elderly, sicker, or unvaccinated, according to Strahm.

“With Omicron still dominant globally today, our results should provide reassurance to those who are contracting COVID-19 for the first time, as well as those who have already had the wild-type virus,” Strahm said in the press release.

Reference

European Society of Clinical Microbiology and Infectious Disease. Long Covid is much less likely after omicron than after variant circulating at start of COVID-19 pandemic. News Release. March 8, 2023. Accessed March 9, 2023. https://www.eurekalert.org/news-releases/981916