Elke Wynberg

Chapter 4 102 number of participants in follow-up at that point, and was compared by clinical severity group. Asymptomatic participants contributed to the denominator. Given the potential recall bias in reporting symptom onset, we restricted this analysis to prospectivelyenrolled participants. For symptoms reported by >20% of participants at 12 weeks after symptom onset, changes in self-reported symptom severity over time during the acute phase were visualised using transition plots, stratified by clinical severity group. The proportion of participants with ongoing symptoms (overall and for each symptom separately) were estimated using Kaplan-Meier survival curves using data from both prospectively- and retrospectively-enrolled participants. The at-risk period began at illness onset and continued until symptom recovery, loss to follow up, 12 months after illness onset, date of first vaccination (to omit any effect of vaccination on time to recovery), or last study visit prior to 1 June 2021 (i.e. administrative censor date), whichever occurred first. Asymptomatic participants were excluded from all symptom survival analysis. Analysis of determinants associated with time to recovery from symptoms is described in Supplementary Methods. A p<0.05 was considered statistically significant. Statistical analyses were performed using Stata (StataCorp, v.15.1) and R (RStudio, v.1.2.5033). RESULTS Study population Participant enrolment and follow-up is summarised in Supplementary Figure S1. Between 11 May 2020 and 1 May 2021, 342 participants were enrolled, most (251/343;73%) prospectively. Of these 342, 99 (29%) experienced mild, 145 (42%) moderate, 56 (16%) severe and 42 (12%) critical disease (Table 1). All participants had prior confirmation of SARS-CoV-2 infection by PCR or antigen testing upon enrolment; none were enrolled solely on the basis of SARS-CoV-2-specific antibodies. Participants with severe or critical disease were older than those with mild or moderate disease (p<0.001), had higher BMI (p<0.001) and more frequently had a diagnosis of CVD, CLD, or DM (Table 1). Median time from illness onset to enrolment was 9 days (IQR=5-14) for prospectively enrolled and 85 days (IQR=7294) for retrospectively enrolled participants. Until 1 June 2021, 66 participants were lost to follow-up. Two deaths, both due to COVID-19, occurred during follow-up.

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