There is a paucity of data on the natural trajectory of outcomes in survivors of COVID-19 beyond 2 years after symptom onset, and no evidence exists on the effect of re-infection in people with long COVID symptoms. We aimed to investigate the 3-year health outcomes of COVID-19 survivors and the effect of omicron re-infection.

In this single-centre, longitudinal cohort study, we recruited participants with confirmed COVID-19 who were discharged from the Jin Yin-tan hospital in Wuhan, China, between Jan 7 and May 29, 2020. Participants completed three follow-up visits at 6 months (June 16 to Sept 13, 2020), 1 year (Dec 16, 2020, to Feb 7, 2021), and 2 years (Nov 16, 2021, to Jan 10, 2022) since symptom onset (reported previously). At 1-year follow-up, community controls without a history of SARS-CoV-2 infection were recruited from two communities in Wuhan and at 2 years were matched (1:1) with survivors of COVID-19 who underwent pulmonary function tests. We did a 3-year follow-up from Feb 23, 2023, to April 20, 2023, after the omicron (B.1.1.529) wave in winter, 2022. All eligible survivors of COVID-19 and community controls matched at 2-year follow-up were invited to the outpatient clinic at the hospital to complete several face-to-face questionnaires, a 6-min walking test (6MWT), and laboratory tests. A subgroup of survivors of COVID-19 identified by stratified sampling on the basis of disease severity scale score during hospitalisation and community controls underwent pulmonary function tests. Survivors of COVID-19 who received high-resolution CT and showed abnormal lung images at 2-year follow-up were invited for another assessment. We identified participants with and without long COVID at 2 years. The primary outcomes were sequelae symptoms, omicron infection, lung function, and chest imaging at the 3-year follow-up.

Of 1359 COVID-19 survivors who completed 2-year and 3-year follow-up, 728 (54%) had at least one sequelae symptom at 3 years after symptom onset and before omicron infection, mainly mild to moderate severity. During the omicron wave, participants with long COVID at 2 years had a significantly higher proportion of re-infection (573 [76%] of 753 vs 409 [67%] of 606 without long COVID; p=0·0004), pneumonia (27 [5%] of 568 vs seven [2%] of 403; p=0·012). 3 months after omicron infection, 126 (62%) of 204 survivors with long COVID at 2 years had newly occurring or worse symptoms, which was significantly higher than the proportion in the non-long COVID group (85 [41%] of 205; p<0·0001) and community controls (81 [40%] of 205; p<0·0001), and not significantly different between COVID-19 survivors without long COVID and matched community controls (85 [41%] of 205 vs 81 [39%] of 206; p=0·66). Re-infection was a risk factor for dyspnoea (odds ratio 1·36 [95% CI 1·04 to 1·77]; p=0·023), anxiety or depression (OR 1·65 [1·24 to 2·20]; p=0·0007), EuroQol visual analogue scale score (β –4·51 [–6·08 to –2·95]; p<0·0001), but not for reduced daily activity (0·72 [0·38 to 1·37]; p=0·32) at 3 years. Lung function of survivors at 3 years was similar to that of matched community controls. We found irregular line, traction bronchiectasis, subpleural lines and ground glass opacity at 3 years, but the volume ratio of lung lesion to total lung was only 0·2–0·3%.