Overall, regardless of initial disease severity, the nearly 2,500 COVID-19 survivors in the study had improvements in physical and mental health over time.

Nearly 90% of those who were employed returned to their jobs within two years. But the survivors had a "remarkably" lower health status than the general population at two years, and their burden of symptoms from after-effects "remained fairly high," the researchers reported on this week in The Lancet Respiratory Diseases.

At two years, 55% still had at least one COVID-19 after-effect, according to the report. Fatigue or muscle weakness were the most frequently reported symptoms during the study.

Patients who had required mechanical ventilation for critical illness still had high rates of lung impairments at two years.