More than 50% of long-COVID patients failed to improve 1.5 years after their initial diagnosis, according to a new study based on cases seen at a Danish post-COVID clinic, both before and after the Omicron variant period. The study was published yesterday in the International Journal of Infectious Diseases.
The analysis included 806 patients who were infected with the wild-type strain, Alpha, Delta, or Omicron strain. All case-patients had been referred to a long COVID clinic with symptoms persisting at least 12 weeks from onset of COVID-19. Seventy percent of participants were female, with a median age of 48.
Patients were given a post-COVID symptom questionnaire (PCQ), and standard health scores, four times between enrollment and 18 months of follow-up. The first clinic visit for long COVID occurred an average of 7 months after acute infection. Patients were grouped according to the period of transmission of predominant SARS-CoV-2 variants, with 69% of patients infected during the wild-type period and 9%, 7%, and 15% infected in the Alpha, Delta, and Omicron periods, respectively.
Omicron patients had lower quality of life
The authors found that patients infected in the Delta period had significantly more severe long COVID initially, with a mean PCQ score of 43, compared with 38 for patients infected in the wild-type period.
Patients infected in the Omicron period did not differ in PCQ score (median 40) compared to wild-type patients (median 38) or to pre-Omicron patients (median 38). However, patients infected with Omicron had a lower health-related quality of life compared to patients infected with wild-type strain.
At 1.5 year after infection, patients had no clinically meaningful decline in severity of long COVID.
"At 1.5 year after infection, patients had no clinically meaningful decline in severity of long COVID, and 57% (245/429) of patients failed to improve 1.5 years after infection, with no differences between variants," the authors wrote.
Overall, PCQ scores fell 7 to 10 months post-infection, then plateaued between 10 and 18 months, Overall median PCQ score declined from 38 at 7 months to 33 at 18-month follow-up.
"In some patients, long COVID may last for more than 2 years after infection, which is supported by our data," the authors concluded.