In a prospective 6-month follow-up of hospitalized COVID-19 patients (N=146, mean age 64 years), 9.6% and 7.8% reported moderate/severe persistent symptoms at 2 and 6 months, respectively (García-Abellán et al. medRxiv preprint, 8 March). Risk factors for persistent symptoms at 6 months were female sex, and a less robust humoral response during the acute phase, as shown by lower peak IgG antibody plasma levels against the CoV-2 surface S1 domain of the spike protein. Long COVID symptoms included persistent fatigue, headache, dyspnea and anosmia. A separate study of patients’ self-reported symptoms found that 13.3% had symptom duration >28 days, 4.5% for >8 weeks and 2.3% for >12 weeks (Sudre et al. medRxiv preprint, 19 December 2020).
Long COVID appears to be more common in children. A study of 129 children (mean age 11 years) found that 52.7% had at least one persistent symptom >120 days post-infection; 22.5% had three or more symptoms (Buonsenso et al. medRxiv preprint, 26 January 2021). The most common symptoms were insomnia, respiratory, nasal congestion, fatigue, and muscle or joint pain.