The conditions that linger after recovery from COVID-19 are commonly referred to as the long-term effects of COVID-19 (long COVID). The risk for sequelae varies according to the severity of the initial acute SARS-CoV-2 infection.1
We note that the proportion of patients admitted to intensive care units included in Lixue Huang and colleagues’ analysis of 1-year outcomes in hospital survivors with COVID-19 was small (4%) and might not realistically capture the repercussions of long COVID. Furthermore, patients with comorbid activity-limiting health conditions or disabilities, a patient demographic previously shown to have an increased prevalence of long COVID by the UK Office for National Statistics, were excluded.3
Anxiety or depression were observed infrequently in patients at both 6 months (23%) and 12 months (26%). Self-reported symptoms of depression might be misleading and overestimate the actual prevalence. This overestimation might explain why only one patient with COVID-19 reported participation in a psychological intervention programme.2 In the future, the investigators might consider using questionnaires specific to depression and anxiety to avoid this issue.
Cytokines are closely associated with the progression and severity of chronic fatigue syndrome.4 Given the high rate of fatigue and weakness and the availability of data on cytokines, are the investigators able to compare the difference in the number of survivors between patients with fatigue or muscle weakness and those without fatigue or muscle weakness?
Lastly, reinfection with SARS-CoV-2 variants have been confirmed with genetic evidence.5 It is unclear whether patients with long COVID also have an increased susceptibility to reinfection because of the poor durability of their antibody response. Despite the success of COVID-19 vaccines, their effectiveness in preventing long COVID has yet to be elucidated.
SJT reports a grant from the Canadian Institutes of Health Research. All other authors declare no competing interests.
References
- 1.Al-Aly Z, Xie Y, Bowe B. High-dimensional characterization of post-acute sequelae of COVID-19. Nature. 2021;594:259–264. doi: 10.1038/s41586-021-03553-9. [DOI] [PubMed] [Google Scholar]
- 2.Huang L, Yao Q, Gu X, et al. 1-year outcomes in hospital survivors with COVID-19: a longitudinal cohort study. Lancet. 2021;398:747–758. doi: 10.1016/S0140-6736(21)01755-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.The UK Office for National Statistics Prevalence of ongoing symptoms following coronavirus (COVID-19) infection in the UK: 1 July 2021. July 1, 2021. https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/bulletins/prevalenceofongoingsymptomsfollowingcoronaviruscovid19infectionintheuk/1july2021
- 4.Yang T, Yang Y, Wang D, et al. The clinical value of cytokines in chronic fatigue syndrome. J Transl Med. 2019;17:213. doi: 10.1186/s12967-019-1948-6. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.To KK-W, Hung IF-N, Ip JD, et al. COVID-19 re-infection by a phylogenetically distinct SARS-coronavirus-2 strain confirmed by whole genome sequencing. Clin Infect Dis. 2020 doi: 10.1093/cid/ciaa1275. published online Aug 25. [DOI] [PMC free article] [PubMed] [Google Scholar]