Tag: long covid vs ME/CFS

No Causal Effects Detected in COVID-19 and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Two Sample Mendelian Randomization Study

Abstract

New clinical observational studies suggest that Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a sequela of COVID-19 infection, but whether there is an exact causal relationship between COVID-19 and ME/CFS remains to be verified. To investigate whether infection with COVID-19 actually causes ME/CFS, this paper obtained pooled data from the Genome Wide Association Study (GWAS) and analyzed the relationship between COVID susceptibility, hospitalization and severity of COVID and ME/CFS, respectively, using two-sample Mendelian randomization (TSMR).
TSMR analysis was performed by inverse variance weighting (IVW), weighted median method, MR-Egger regression and weighted mode and simple mode methods, respectively, and then the causal relationship between COVID-19 and ME/CFS was further evaluated by odds ratio (OR). Eventually, we found that COVID-19 severity, hospitalization and susceptibility were all not significantly correlated with ME/CFS (OR:1.000,1.000,1.000; 95% CI:0.999–1.000, 0.999–1.001, 0.998–1.002; p = 0.333, 0.862, 0.998, respectively). We found the results to be reliable after sensitivity analysis.
These results suggested that SARS-CoV-2 infection may not significantly contribute to the elevated risk of developing CFS, and therefore ME/CFS may not be a sequela of COVID-19, but may simply present with symptoms similar to those of CFS after COVID-19 infection, and thus should be judged and differentiated by physicians when diagnosing and treating the disease in clinical practice.
Source: Xu W, Cao Y, Wu L. No Causal Effects Detected in COVID-19 and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Two Sample Mendelian Randomization Study. International Journal of Environmental Research and Public Health. 2023; 20(3):2437. https://doi.org/10.3390/ijerph20032437 https://www.mdpi.com/1660-4601/20/3/2437 (Full text)

Improvement of Long COVID symptoms over one year

Abstract:

Importance: Early and accurate diagnosis and treatment of Long COVID, clinically known as post-acute sequelae of COVID-19 (PASC), may mitigate progression to chronic diseases such as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Our objective was to determine the utility of the DePaul Symptom Questionnaire (DSQ) to assess the frequency and severity of common symptoms of ME/CFS, to diagnose and monitor symptoms in patients with PASC.

Methods: This prospective, observational cohort study enrolled 185 people that included 34 patients with PASC that had positive COVID-19 test and persistent symptoms of >3 months and 151 patients diagnosed with ME/CFS. PASC patients were followed over 1 year and responded to the DSQ at baseline and 12 months. ME/CFS patients responded to the DSQ at baseline and 1 year later. Changes in symptoms over time were analyzed using a fixed-effects model to compute difference-in-differences estimates between baseline and 1-year follow-up assessments.

Participants: Patients were defined as having PASC if they had a previous positive COVID-19 test, were experiencing symptoms of fatigue, post-exertional malaise, or other unwellness for at least 3 months, were not hospitalized for COVID-19, had no documented major medical or psychiatric diseases prior to COVID-19, and had no other active and untreated disease processes that could explain their symptoms. PASC patients were recruited in 2021. ME/CFS patients were recruited in 2017.

Results: At baseline, patients with PASC had similar symptom severity and frequency as patients with ME/CFS and satisfied ME/CFS diagnostic criteria. ME/CFS patients experienced significantly more severe unrefreshing sleep and flu-like symptoms. Five symptoms improved significantly over the course of 1 year for PASC patients including fatigue, post-exertional malaise, brain fog, irritable bowel symptoms and feeling unsteady. In contrast, there were no significant symptom improvements for ME/CFS patients.

Conclusion and relevance: There were considerable similarities between patients with PASC and ME/CFS at baseline. However, symptoms improved for PASC patients over the course of a year but not for ME/CFS patients. PASC patients with significant symptom improvement no longer met ME/CFS clinical diagnostic criteria. These findings indicate that the DSQ can be used to reliably assess and monitor PASC symptoms.

Source: Oliveira CR, Jason LA, Unutmaz D, Bateman L, Vernon SD. Improvement of Long COVID symptoms over one year. Front Med (Lausanne). 2023 Jan 9;9:1065620. doi: 10.3389/fmed.2022.1065620. PMID: 36698810; PMCID: PMC9868805. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9868805/ (Full text)

Long-COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): Potential neurophysiological biomarkers for these enigmatic entities

Since early in the pandemic, fatigue has been recognized as one of the most common persistent complaints in individuals infected with SARS-CoV-2, and constitutes one main symptom of the so-called long-COVID syndrome. The term fatigue refers to a sustained feeling of tiredness, which can be present at rest; it is not directly related to physical activity, but can be exacerbated disproportionally by exertion.

Survivors of other recent coronavirus outbreaks, such as severe acute respiratory syndrome (SARS) in 2002 and Middle East respiratory syndrome (MERS) in 2012 also developed chronic fatigue. These ‘post-infectious’ fatigue syndromes, including long-COVID, resemble myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a chronic disorder of unknown physiopathology characterized by fatigue, post-exertional malaise, chronic muscle or skeletal pain, and cognitive impairment (‘brain fog’).

Despite it being an extremely disabling symptom, the results of routine examinations are often normal in patients complaining of lingering fatigue, a phenomenon that has also led the medical-scientific community to view this condition with skepticism.

In physiology, fatigue is defined as a decrease in the maximal force-generating capacity of a muscle during exercise. It may result from peripheral processes distal to the neuromuscular junction and from central processes controlling the discharge rate of motoneurons.

Physical fatigue related to both central and peripheral nervous system dysfunction can be assessed with neurophysiological techniques including transcranial magnetic stimulation (TMS) of the motor cortex, electrical stimulation of nerve trunks or intramuscular nerve fibers, and electromyography (EMG) recordings.

In August 2021, the first study showing myopathic changes in quantitative EMG (qEMG) in long-COVID patients with musculoskeletal symptoms was published (). The same authors demonstrated myopathic qEMG features and histopathological changes in skeletal muscle biopsies in 16 patients with complaints of fatigue, myalgia, and/or weakness persisting for up to 14 months after mild to moderate COVID-19 (). The wide variety of histological changes in this study, including muscle fiber atrophy, mitochondrial changes, subsarcolemmal accumulation, inflammation, capillaries alteration, suggests that skeletal muscle may be a major target of SARS-CoV-2.

On the opposite side of the neuroaxis, dysfunction in the activity of the primary motor cortex and reduced corticomotor output may underlie fatigue.

The first TMS study on motor cortex physiology was conducted on 12 patients with long-term fatigue and ‘brain fog’ after severe COVID-19 (). It showed disruption of the physiological mechanism of post-contraction depression, i.e., the transient decrease in the amplitude of motor evoked potentials and prolongation of the cortical silent period after a fatiguing motor task, which depends on cortical inhibitory mechanisms and has the protective purpose of preventing muscle overload. Impairment of intracortical GABAergic activity, as indicated by disrupted long-interval intracortical inhibition, together with reduced excitability of the primary motor cortex was subsequently demonstrated in 67 patients with fatigue and cognitive difficulties after mild COVID-19 (). These patients also presented selective deficits in executive functions. Based on these findings, the authors proposed that fatigue depends on altered excitability and neurotransmission within the motor cortex at rest, and on abnormal reactivity to muscular exercise. In addition, reduced executive control may contribute to exacerbating poor physical performance and fatigue tolerance ().

These objective neurophysiological and histopathological findings showed for the first time that fatigue may due both to pathological processes in the muscle (the effector of the motor command) and/or at the site of motor command processing. The mechanisms of chronic dysfunction of neural and muscle cells may be sustained by inflammation or dysimmunity, triggered by SARS-COV-2 in predisposed individuals.

Immune-inflammatory and neuroendocrine mechanisms have also been implicated in ME/CFS. In particular, increased production of autoantibodies against CNS and autonomic nervous system targets, such as the ß2 adrenergic receptor (ß2AdR), have been documented (). As ß2AdR are important vasodilators, their functional disturbance may result in vasoconstriction and hypoxemia with chronic muscular and cerebral hypoperfusion.

The COVID-19 pandemic is likely to greatly increase the incidence of ME/CFS, so that the intense research on the pathophysiological mechanisms of fatigue in long-COVID can help to shed light on a poorly understood and underestimated syndrome.

Source: Versace V, Tankisi H. Long-COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): Potential neurophysiological biomarkers for these enigmatic entities. Clin Neurophysiol. 2023 Jan 13;147:58-59. doi: 10.1016/j.clinph.2023.01.001. Epub ahead of print. PMID: 36657309; PMCID: PMC9838078. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9838078/ (Full text)

Converging Evidence of Similar Symptomatology of ME/CFS and PASC Indicating Multisystemic Dyshomeostasis

Abstract:

The purpose of this article is to review the evidence of similar symptomatology of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and post-acute sequelae of SARS-CoV-2 infection (PASC).
Reanalysis of data from a study by Jason comparing symptom reports from two groups of ME/CFS and PASC patients shows a notably similar symptomatology. Symptom scores of the PASC group and the ME/CFS group correlated 0.902 (p < 0.0001) across items. The hypothesis is presented that ME/CFS and PASC are caused by a chronic state of multisystemic disequilibrium including endocrinological, immunological, and/or metabolic changes.
The hypothesis holds that a changed set point persistently pushes the organism towards a pathological dysfunctional state which fails to reset. To use an analogy of a thermostat, if the ‘off switch’ of a thermostat intermittently stops working, for periods the house would become warmer and warmer without limit. The hypothesis draws on recent investigations of the Central Homeostasis Network showing multiple interconnections between the autonomic system, central nervous system, and brain stem.
The hypothesis helps to explain the shared symptomatology of ME/CFS and PASC and the unpredictable, intermittent, and fluctuating pattern of symptoms of ME/CFS and PASC. The current theoretical approach remains speculative and requires in-depth investigation before any definite conclusions can be drawn.
Source: Marks DF. Converging Evidence of Similar Symptomatology of ME/CFS and PASC Indicating Multisystemic Dyshomeostasis. Biomedicines. 2023; 11(1):180. https://doi.org/10.3390/biomedicines11010180 https://www.mdpi.com/2227-9059/11/1/180 (Full text)

Orthostatic Intolerance after COVID-19 Infection: Is Disturbed Microcirculation of the Vasa Vasorum of Capacitance Vessels the Primary Defect?

Abstract:

Following COVID-19 infection, a substantial proportion of patients suffer from persistent symptoms known as Long COVID. Among the main symptoms are fatigue, cognitive dysfunction, muscle weakness and orthostatic intolerance (OI). These symptoms also occur in myalgic encephalomyelitis/chronic fatigue (ME/CFS).
OI is highly prevalent in ME/CFS and develops early during or after acute COVID-19 infection. The causes for OI are unknown and autonomic dysfunction is hypothetically assumed to be the primary cause, presumably as a consequence of neuroinflammation. Here, we propose an alternative, primary vascular mechanism as the underlying cause of OI in Long COVID.
We assume that the capacitance vessel system, which plays a key role in physiologic orthostatic regulation, becomes dysfunctional due to a disturbance of the microvessels and the vasa vasorum, which supply large parts of the wall of those large vessels. We assume that the known microcirculatory disturbance found after COVID-19 infection, resulting from endothelial dysfunction, microthrombus formation and rheological disturbances of blood cells (altered deformability ), also affects the vasa vasorum to impair the function of the capacitance vessels.
In an attempt to compensate for the vascular deficit, sympathetic activity overshoots to further worsen OI, resulting in a vicious circle that maintains OI. The resulting orthostatic stress, in turn, plays a key role in autonomic dysfunction and the pathophysiology of ME/CFS.
Source: Wirth KJ, Löhn M. Orthostatic Intolerance after COVID-19 Infection: Is Disturbed Microcirculation of the Vasa Vasorum of Capacitance Vessels the Primary Defect? Medicina. 2022; 58(12):1807. https://doi.org/10.3390/medicina58121807 https://www.mdpi.com/1648-9144/58/12/1807 (Full text)

ME/CFS and Post-Exertional Malaise among Patients with Long COVID

Abstract:

This study sought to ascertain the prevalence of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) among a sample of 465 patients with Long COVID. The participants completed three questionnaires: (1) a new questionnaire measuring both the frequency and severity of 38 common symptoms of COVID and Long COVID, (2) a validated short form questionnaire assessing ME/CFS, and (3) a validated questionnaire measuring post-exertional malaise.
The population was predominantly white, female, and living in North America. The mean duration since the onset of COVID-19 symptoms was 70.5 weeks. Among the 465 participants, 58% met a ME/CFS case definition. Of respondents who reported that they had ME/CFS only 70.57% met criteria for ME/CFS and of those who did not report they had ME/CFS, 29.43% nevertheless did meet criteria for the disease: both over-diagnosis and under-diagnosis were evident on self-report. This study supports prior findings that ME/CFS occurs with high prevalence among those who have persistent COVID-19 symptoms.
Source: Jason LA, Dorri JA. ME/CFS and Post-Exertional Malaise among Patients with Long COVID. Neurology International. 2023; 15(1):1-11. https://doi.org/10.3390/neurolint15010001 https://www.mdpi.com/2035-8377/15/1/1 (Full text)

Brain fog of post-COVID-19 condition and Chronic Fatigue Syndrome, same medical disorder?

Abstract:

Background: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is characterized by persistent physical and mental fatigue. The post-COVID-19 condition patients refer physical fatigue and cognitive impairment sequelae. Given the similarity between both conditions, could it be the same pathology with a different precipitating factor?

Objective: To describe the cognitive impairment, neuropsychiatric symptoms, and general symptomatology in both groups, to find out if it is the same pathology. As well as verify if the affectation of smell is related to cognitive deterioration in patients with post-COVID-19 condition.

Methods: The sample included 42 ME/CFS and 73 post-COVID-19 condition patients. Fatigue, sleep quality, anxiety and depressive symptoms, the frequency and severity of different symptoms, olfactory function and a wide range of cognitive domains were evaluated.

Results: Both syndromes are characterized by excessive physical fatigue, sleep problems and myalgia. Sustained attention and processing speed were impaired in 83.3% and 52.4% of ME/CFS patients while in post-COVID-19 condition were impaired in 56.2% and 41.4% of patients, respectively. Statistically significant differences were found in sustained attention and visuospatial ability, being the ME/CFS group who presented the worst performance. Physical problems and mood issues were the main variables correlating with cognitive performance in post-COVID-19 patients, while in ME/CFS it was anxiety symptoms and physical fatigue.

Conclusions: The symptomatology and cognitive patterns were similar in both groups, with greater impairment in ME/CFS. This disease is characterized by greater physical and neuropsychiatric problems compared to post-COVID-19 condition. Likewise, we also propose the relevance of prolonged hyposmia as a possible marker of cognitive deterioration in patients with post-COVID-19.

Source: Azcue N, Gómez-Esteban JC, Acera M, Tijero B, Fernandez T, Ayo-Mentxakatorre N, Pérez-Concha T, Murueta-Goyena A, Lafuente JV, Prada Á, López de Munain A, Ruiz-Irastorza G, Ribacoba L, Gabilondo I, Del Pino R. Brain fog of post-COVID-19 condition and Chronic Fatigue Syndrome, same medical disorder? J Transl Med. 2022 Dec 6;20(1):569. doi: 10.1186/s12967-022-03764-2. PMID: 36474290. https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-022-03764-2 (Full text)

The Prevalence, Severity, and Impact of Post-COVID Persistent Fatigue, Post-Exertional Malaise, and Chronic Fatigue Syndrome

Background: Fatigue is common after viral infections, including SARS-CoV-2.1 Our purpose was to report the prevalence and impact of persistent fatigue 6 months after SARS-CoV-2 infection, considering post-exertional malaise2 and criteria for chronic fatigue syndrome.3

Methods: Since March 2020, individuals tested for SARS-CoV-2 at the Geneva University Hospitals outpatient testing center benefit from remote ambulatory follow-up (COVICARE). This study included all individuals tested between March 2020 and December 2020 and whose follow-up was at 6 months or more after their test date.

Follow-up included questions about the prevalence of symptoms (yes/no) and their severity using a Likert scale (mild, moderate, or severe). Fatigue was assessed using the Eastern Cooperative Oncology Group (ECOG) scale and the Chalder fatigue scale. The Chalder fatigue scale was scored using the 4-item Likert and the bimodal scoring schemes. A score of ≥ 4 on bimodal scoring indicated severe fatigue.

The DePaul brief questionnaire was used to identify post-exertional malaise and criteria for chronic fatigue syndrome.

The Sheehan Disability Scale was used to assess functional impairment. Reduced work capacity was defined as missing days off work or having a reduced productivity on the Sheehan disability scale.

Comorbidities were considered present if pre-existing prior to SARS-CoV-2 infection. Statistical analysis included descriptive comparisons of percentages using chi-square tests and Student’s t test.

Results: Overall, 5515 individuals participated in this study (response rate 70.7%), with 5406 participants at 6 months or more after their test date. A total of 1497 (27.7%) participants had a documented positive SARS-CoV-2 test and were ultimately included in the study. The median time for follow-up was 225 days (interquartile range 207–398). Respectively, fatigue was reported by 17.2%, post-exertional malaise by 8.2%, and the presence of criteria for chronic fatigue syndrome by 1.1% of SARS-CoV-2-positive individuals, compared to 8.9%, 3.5%, and 0.5% of SARS-CoV-2-negative individuals. Characteristics are presented in Table 1.

Out of SARS-CoV-2-positive participants with fatigue (n = 258), 35.3% had moderate to severe limitations on the ECOG scale, and 83.0% had a score ≥ 4 on the Chalder fatigue scale. The Chalder fatigue scale revealed a mean score of 19 out of 33, SD 5.4, and a mean score of 6.7 out of 11, SD 3.3 using bimodal scoring. After adjusting for age and sex, 47.7% of SARS-CoV-2-positive individuals with fatigue at 6 months or more had the frequency and severity criteria for post-exertional malaise, and 6.2% had criteria for chronic fatigue syndrome.

Individuals had a higher prevalence of insomnia, cognitive impairment, headaches, generalized pain, functional impairment, reduced work capacity, and decreased physical activity, after SARS-CoV-2 infection. The prevalence of these sequelae was adjusted for age and sex and was increasingly higher with severe fatigue, with post-exertional malaise, or when criteria for chronic fatigue syndrome were present (Fig. 1).

Discussion: Fatigue is the most common and persistent post-COVID symptom. The spectrum of fatigue severity in post-COVID individuals ranges from feeling tired to having severe fatigue, post-exertional malaise, or criteria for chronic fatigue syndrome with an increasing impact on health, functional capacity, and physical activity.

Almost half of individuals experiencing fatigue at 6 months after the infection had post-exertional malaise, and 6.2% had criteria for chronic fatigue syndrome, prompting physicians to consider pacing as a management option, in the absence of other treatment options at this stage. SARS-CoV-2 infection was positively associated with fatigue and post-exertional malaise.

Results showed that individuals with fatigue were more likely to be vaccinated. This was partially explained by the baseline distribution as older individuals and those with more comorbidities were more likely to get vaccinated.

Results compare to recent reviews showing an overlap between post-COVID condition and chronic fatigue syndrome. Our study graded post-COVID fatigue by severity in correlation with functional capacity, and showed the high prevalence of post-exertional malaise.

Limitations include the self-reported nature of this follow-up with individuals infected in 2020 and follow-up in 2021, lacking comparisons to individuals infected with other variants. Additionally, this study considered having received at least 2 doses as full vaccination, a concept that continues to evolve with time.

Physicians, employers, and insurance companies should address fatigue on a spectrum, accounting for the correlated functional impairment, decreased activity levels, and potentially poorer quality of life.

Source: Nehme M, Chappuis F, Kaiser L, Assal F, Guessous I. The Prevalence, Severity, and Impact of Post-COVID Persistent Fatigue, Post-Exertional Malaise, and Chronic Fatigue Syndrome. J Gen Intern Med. 2022 Nov 10:1–5. doi: 10.1007/s11606-022-07882-x. Epub ahead of print. PMID: 36357723; PMCID: PMC9648889. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9648889/ (Full text)

 

Global prevalence of chronic fatigue syndrome among long COVID-19 patients: A systematic review and meta-analysis

Abstract:

Background: Chronic fatigue syndrome is a persistent and debilitating disorder. According to several studies, chronic fatigue syndrome has been identified among recovered COVID-19 patients as the most common symptom of long COVID. The aim of this systematic review and meta-analysis study was to obtain the prevalence of chronic fatigue syndrome in long COVID cases.

Methods: In this systematic review and meta-analysis, we analysed reported results of studies that assessed the occurrence of chronic fatigue syndrome among COVID-19 patients four weeks after the onset of symptoms. The study selection was commenced by searching PubMed, Web of Science, Science Direct, Scopus, Embase, and Google scholar using the keywords of Chronic fatigue syndrome, COVID-19, and post-COVID-19 syndrome. The searches were without a lower time limit and until April 2022. Heterogeneity of studies was assessed using the I2 index, and a random effects model was used for analysis. Data analysis was performed within the Comprehensive Meta-Analysis software (version 2).

Results: The pooled prevalence of chronic fatigue syndrome four weeks after the onset of COVID-19 symptoms, in 52 studies with a sample size of 127,117, was 45.2% (95% CI: 34.1-56.9%). Meta-regression analysis in examining the effects of the two factors of sample size, and year of study on the changes in the overall prevalence, showed that with increasing sample size, and year of study, the prevalence of chronic fatigue syndrome among long COVID patients (p < 0.05).

Conclusion: Our results show that the overall prevalence of chronic fatigue syndrome as a long COVID symptom is 45.2%. Chronic fatigue after infection with COVID-19 can negatively affect personal and social lives. Given such significant negative consequences caused by the syndrome, it is recommended that health policymakers allocate funds to reduce the adverse effects of this syndrome, by creating programs to support long COVID patients.

Source: Salari N, Khodayari Y, Hosseinian-Far A, Zarei H, Rasoulpoor S, Akbari H, Mohammadi M. Global prevalence of chronic fatigue syndrome among long COVID-19 patients: A systematic review and meta-analysis. Biopsychosoc Med. 2022 Oct 23;16(1):21. doi: 10.1186/s13030-022-00250-5. PMID: 36274177; PMCID: PMC9589726. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9589726/ (Full text)

Long-haul COVID: heed the lessons from other infection-triggered illnesses

According to the Johns Hopkins Coronavirus Resource Center, more than 115 million people worldwide have been infected with SARS-CoV-2 during the COVID-19 pandemic, with extensive implications for morbidity and mortality. Description of long-term effects of COVID-19 are apparing in the medical literature; the first large cohort study with 6-months’ follow-up has been published, and more data are sure to follow. A small number of studies point not only to persistent imaging and testing abnormalities across several organ systems in the postacute period, but to a high frequency of patient-reported symptoms such as fatigue, insomnia, anxiety and depression, autonomic disturbances, cognitive difficulties, pain, and others. The presence of patient support groups, and the rapid expansion of clinics to manage or treat these symptoms, validate further their existence and impact.
Although the frequency, severity, and potentially the etiology of persistent symptoms can vary, sequelae after COVID-19 appears poised to join the range of other postinfectious syndromes described in the field of infectious diseases.

These often share a common symptom phenotype, which might also meet case definitions for myalgic encephalomyelitis/chronic fatigue syndrome, fibromyalgia, or post-treatment Lyme disease. We hope that researchers and clinicians will draw on these other conditions as they continue to advance scientific understanding of so-called long-haul or persistent COVID-19. We would also argue that there are important lessons to learn and pitfalls to avoid; our specific area of clinical care and research (post-treatment Lyme disease) has remained a fiercely contentious condition for more than 30 years.

Read the rest of this article HERE.
Source: John N Aucott, Alison W Rebman. Long-haul COVID: heed the lessons from other infection-triggered illnesses. The Lancet, CORRESPONDENCE| VOLUME 397, ISSUE 10278, P967-968, MARCH 13, 2021 https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00446-3/fulltext (Full text)