Prognosis and antibody profiles in survivors of critical illness from COVID-19: a prospective, multi-centre, cohort study

Abstract Background There is a need to assess the long-term outcomes of survivors from critically ill COVID-19. Methods Ninety-two critically ill survivors of COVID-19 from four hospitals in Hubei province, China participated in this prospective cohort study. Multiple characteristics including lung function (lung volumes, diffusing capacity of lung for carbon monoxide, chest CT scores and walking capacity), immune status (SARS-COV-2 neutralizing antibody and all sub-types of IgG against SARS-CoV-2, immune cells in response to ex-vivo antigen peptide stimuli, lymphocyte count and its sub-type), liver, coagulation and kidney function, quality of life, cognitive function and mental status were assessed after 3, 6 and 12-months of follow-up. Results Among the 92 enrolled survivors, 72 (78%) patients required mechanical ventilation. At 12 months, the predicted percentage diffusing capacity of lung for carbon monoxide was 82% (IQR, 76%-97%) with a residual volume of 77% (64%-88%). Other lung function parameters and the 6-minute walk test improved gradually over time and were almost back to normal by 12 months. The titers of IgG and neutralizing antibody to COVID-19 remained high at 12 months compared to non-COVID-19 infected controls, although IgG titers decreased significantly from 33.96 AU/ml (IQR, 23.79-74.30) to 14.98 AU/ml (5.75-24.30) (P Conclusions Critically ill COVID-19 survivors show some persistent long-term impairments in lung function, however the majority of these tests are normal by 12 months. These patients still have detectable levels of neutralising antibodies against SARS-COV-2 and all types of IgG at 12 months, but the levels had declined over this time period.