Systematic review of post-COVID condition in Nordic population-based registry studies.

The long-term effects of COVID-19, known as post-COVID condition (PCC), are still not fully understood. This systematic review synthesizes findings from Nordic registry studies to highlight long-term outcomes after COVID-19 infection. Twenty-two studies, primarily reflecting the pre-omicron and early vaccination phases, reveal increased primary care use for respiratory issues and fatigue in the sub-acute and chronic phases, with PCC incidence estimated below 2% in the general population. Most individuals returned to work within three months post-infection, and the risk of new neurological or mental disorders did not exceed that in patients with other infections. The review demonstrates the value of high-quality Nordic health registries in capturing reliable, population-wide data, though generalizability may be limited to similar healthcare systems. Findings suggest the need for targeted follow-up in patients with severe COVID-19, particularly those requiring intensive care, to manage potential new-onset diseases and guide resource allocation in the pandemic's endemic phase.