Fig. 2. Six-month follow-up of patients with COVID-19 in Bergen, Norway.

The relationship of severity of initial COVID-19 illness and of age with anti-SARS-CoV-2 spike (a and b) and microneutralizing antibody titers (e and f) at 2 months. The relationship of antibody titers at 2 months with number of persistent symptoms (c and g) and total fatigue score according to the Chalder scale (d and h) at 6-month follow-up. The 13 symptoms used are listed in Table 2. The severity of illness was as follows: 1—asymptomatic (n = 5); 2—home-isolated with symptoms (n = 242); 3—hospitalized without medical needs (n = 0); 4—hospitalized with medical needs (n = 31); 5—hospitalized needing O₂ (n = 24); 6—hospitalized needing non-invasive ventilation (n = 4); and 7—hospitalized needing respirator (n = 6). The cohort was divided into 15-year age groups: 0–15 (n = 16), 16–30 (n = 65), 31–45 (n = 69), 46–60 (n = 90) and >60 (n = 72). a, b, e and f show median spike IgG and microneutralizing antibody titers (horizontal line), 25% and 75% quantiles (box), plus 95% confidence intervals (lines) with outliers (dots). c and d are violin plots of number of symptoms (up to 13) or fatigue score (values 0–33) divided into four categories of spike IgG: <150 (n = 21), 150–4999 (n = 96), 5,000–20,000 (n = 103) and >20,000 (n = 92). 5k, 5,000; 20k, 20,000. g and h are violin plots of four categories of microneutralizing titers: <20 (neg n = 42), 20–79 (n = 107), 80–320 (n = 92) and >320 (n = 71). O₂, supplemental oxygen.