Long Covid in Year 5: Some Progress, Still Many Questions

Long Covid was first described in 2020. Five years later, progress in disease characterization has been considerable, and definitions continue to evolve. Several disease mechanisms are under study, and evidence for multiple endotypes is accumulating. No clinical biomarker has been identified, nor has an effective therapy been developed. Overlap with other post-infectious syndromes, particularly myalgic encephalomyelitis/chronic fatigue syndrome, is now more evident. For most individuals, symptoms of long Covid progressively disappear over time. Recurrent Covid-19 infections are now an important contributor to the pool of affected individuals. While symptoms limit activity in as many as 20%, inability to work is less common. The anticipated surge of disability claims from insured individuals has not materialized.