SARS-CoV-2 immunity and functional recovery of COVID-19 patients 1-year after infection

Severity Matters: How COVID-19 Severity Impacts Long-Term Effects on Symptoms, Physical Activity and Functionality-An Observational Study

BACKGROUND/OBJECTIVES

The existing literature has described the common symptoms and long-term effects of coronavirus disease (COVID-19). However, there is a lack of detailed information on how different degrees of disease severity affect survivors differently. This study aims to fill that gap by evaluating the symptoms, physical activity, and functionality of COVID-19 survivors across a spectrum of severity levels, comparing them with those of healthy individuals.

METHODS

An observational study was carried out following the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) criteria and checklist. Participants were divided into 5 groups based on COVID-19 severity according to the World Health Organization classification: healthy (COVID-19-negative), mild (symptomatic without pneumonia or dyspnoea), moderate (pneumonia and dyspnoea without hospitalisation), severe (severe pneumonia requiring hospitalisation), and critical (severe pneumonia with admission to the intensive care unit). Descriptive variables, symptoms (Fatigue Borg Scale, Fatigue Impact Scale, Fatigue Severity Scale, Dyspnoea Borg Scale, Visual Analogue Scale, Hospital Anxiety and Depression Scale, and European Quality of Life-5 Dimensions), physical activity (the International Physical Activity Questionnaire) and functionality (Patient-Specific Functional Scale, Short Physical Performance Battery, Arm Curl test, and 2 min step test) were measured.

RESULTS

A total of 304 participants were included: healthy (n = 42), mild (n = 143), moderate (n = 49), severe (n = 52), and critical (n = 18) COVID-19 patients. The impact of COVID-19 on surviving patients varies significantly with the severity of the disease. The results show that the hospitalisation time, age, and comorbidities of the patients are greater in those with a greater severity of the disease. Patients with more severe COVID-19 also experience greater frailty, dysphagia, fatigue, dyspnoea, and pain. Additionally, those with severe cases have poorer overall health, reduced physical activity, and diminished functionality. No evidence of post-COVID-19 anxiety or depression is found in the sample, even considering the timeframe between the negative test and the assessment.

CONCLUSIONS

Patients with higher COVID-19 severity (severe or critical) experience more symptoms than those with lower COVID-19 severity (mild or moderate). Additionally, those with severe cases have poorer overall health, reduced physical activity and diminished functionality. Register: Clinicaltrials.gov: NCT05731817.

Four- and sixteen-month clinical status of a cohort of patients following hospitalization for COVID-19

BACKGROUND AND OBJECTIVES

Although many symptoms of post-COVID syndrome have been described, a comprehensive evaluation of their prevalence is lacking. We aimed to describe symptoms at 16 months from hospitalization for COVID-19.

METHODS

A telephone assessment was performed one year later in a cohort of COVID-19 survivors hospitalized between March and May 2020 and already evaluated four months after discharge. Patients with relevant symptoms at 16 months, patients who presented symptoms at four months, and all intensive care unit patients were invited for assessment at an outpatient facility. At telephone consultation, respiratory, cognitive, and functional symptoms were assessed. Patients underwent pulmonary function tests, lung CT scans, and psychometric and cognitive tests at the outpatient facility.

RESULTS

Among 478 patients evaluated four months after discharge, 317 (67 %) were assessed at telephone consultation and 124 at ambulatory assessment. At telephone assessment, ≥1 new symptom was reported by 216 patients (68 %), mainly fatigue (53 %), dyspnea (37 %), and memory difficulties (24 %). Seventy-nine patients (25 %) were asymptomatic at four months but declared ≥1 symptom one year later. In patients evaluated twice, the prevalence of cognitive impairment was 45 % at four months and 40 % at 16 months. Depression and post-traumatic symptoms prevalence remained stable, and the prevalence of anxiety significantly decreased. Dysfunctional breathing was detected in 32 % of patients. At 16 months after discharge, lung CT-scan exhibited abnormalities in 30/80 patients (38 %), compared to 52/85 patients (61 %) at four months.

CONCLUSION

At 16 months after hospitalization for COVID-19, 68 % of patients declared symptoms, including patients whose symptoms appeared between 4 and 16 months.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04704388.

Immune responses in COVID-19 patients: Insights into cytokine storms and adaptive immunity kinetics

SARS-CoV-2 infection can trigger cytokine storm in some patients, which characterized by an excessive production of cytokines and chemical mediators. This hyperactive immune response may cause significant tissue damage and multiple organ failure (MOF). The severity of COVID-19 correlates with the intensity of cytokine storm, involving elements such as IFN, NF-κB, IL-6, HMGB1, etc. It is imperative to rapidly engage adaptive immunity to effectively control the disease progression. CD4+ T cells facilitate an immune response by improving B cells in the production of neutralizing antibodies and activating CD8+ T cells, which are instrumental in eradicating virus-infected cells. Meanwhile, antibodies from B cells can neutralize virus, obstructing further infection of host cells. In individuals who have recovered from the disease, virus-specific antibodies and memory T cells were observed, which could confer a level of protection, reducing the likelihood of re-infection or attenuating severity. This paper discussed the roles of macrophages, IFN, IL-6 and HMGB1 in cytokine release syndrome (CRS), the intricacies of adaptive immunity, and the persistence of immune memory, all of which are critical for the prevention and therapeutic strategies against COVID-19.

Longitudinal analysis of genomic mutations in SARS-CoV-2 isolates from persistent COVID-19 patient

A primary reason for the ongoing spread of coronavirus disease 2019 (COVID-19) is the continuous acquisition of mutations by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the mechanism of acquiring mutations is not fully understood. In this study, we isolated SARS-CoV-2 from an immunocompromized patient persistently infected with Omicron strain BF.5 for approximately 4 months to analyze its genome and evaluate drug resistance. Although the patient was administered the antiviral drug remdesivir (RDV), there were no acquired mutations in RDV binding site, and all isolates exhibited susceptibility to RDV. Notably, upon analyzing the S protein sequence of the day 119 isolate, we identified mutations acquired by mutant strains emerging from the BF.5 variant, suggesting that viral genome analysis in persistent COVID-19 patients may be useful in predicting viral evolution. These results suggest mutations in SARS-CoV-2 are acquired during long-term viral replication rather than in response to antiviral drugs.

Mapping uterine calcium dynamics during the ovulatory cycle in live mice

Uterine contraction patterns vary during the ovulatory cycle and throughout pregnancy but prior measurements have produced limited and conflicting information on these patterns. We combined a virally delivered genetically encoded calcium reporter (GCaMP8m) and ultra-widefield imaging in live nonpregnant mice to characterize uterine calcium dynamics at organ scale throughout the estrous cycle. Prior to ovulation (proestrus and estrus) uterine excitations primarily initiated in a region near the oviduct, but after ovulation (metestrus and diestrus), excitations initiated at loci homogeneously distributed throughout the organ. The frequency of excitation events was lowest in proestrus and estrus, higher in metestrus and highest in diestrus. These results establish a platform for mapping uterine activity, and show that the question of whether there is an anatomically localized trigger for uterine excitations depends on the estrous cycle phase.

Understanding Patient-Reported Outcome Measures Used in Adult Survivors Experiencing Long-Term Effects After COVID-19 Infection: A Rapid Review

Purpose

Patient-reported outcome measures (PROMs) are used in individuals experiencing long-term effects from COVID-19 infection, or Long COVID, to evaluate the quality of life and functional status of these individuals. However, little is known about which PROMs are being utilised and the psychometric properties of these PROMs. Our purpose was thus to explore which PROMs are used in Long COVID patients and to discuss the psychometric properties of the PROMs.

Methods

For this rapid review, a systematic literature search was performed in the PubMed, Embase, and CINAHL databases. The found studies were screened using the PRISMA flowchart. We then performed study quality appraisal and assessed the psychometric properties of the found PROMs.

Results

Per the systematic literature search and after removal of duplicates, 157 publications were identified for individual screening. After screening and eligibility assessment, 74 articles were selected for our review. In total, 74 PROMs were used and primarily comprised quality of life, fatigue, breathlessness, mental health, and smell/taste issues in COVID "long haulers." Five studies used newly developed, COVID-19-specific PROMs. We assessed the psychometric properties of the 10 most-used PROMs. The majority were found to be reliable and valid instruments. EQ-5D-5L was the most popular and highly rated PROM.

Conclusions

We assessed PROMs used in Long COVID patients and evaluated their psychometric properties. EQ-5D-5L was the most favourably rated PROM. PROMs addressing mental health issues are crucial in managing anxiety and depression in Long COVID patients. New COVID-specific PROMs assess functional status and smell/taste perception and show great utilisation potential in olfactory training at COVID smell clinics. However, many reviewed PROMs currently lack sufficient analysis of their psychometric properties. Therefore, future research needs to examine these measures.

Serological markers and long COVID-A rapid systematic review

BACKGROUND

Long COVID is highly heterogeneous, often debilitating, and may last for years after infection. The aetiology of long COVID remains uncertain. Examination of potential serological markers of long COVID, accounting for clinical covariates, may yield emergent pathophysiological insights.

METHODS

In adherence to PRISMA guidelines, we carried out a rapid review of the literature. We searched Medline and Embase for primary observational studies that compared IgG response in individuals who experienced COVID-19 symptoms persisting ≥12 weeks post-infection with those who did not. We examined relationships between serological markers and long COVID status and investigated sources of inter-study variability, such as severity of acute illness, long COVID symptoms assessed and target antigen(s).

RESULTS

Of 8018 unique records, we identified 29 as being eligible for inclusion in synthesis. Definitions of long COVID varied. In studies that reported anti-nucleocapsid (N) IgG (n = 10 studies; n = 989 participants in aggregate), full or partial anti-Spike IgG (i.e. the whole trimer, S1 or S2 subgroups, or receptor binding domain, n = 19 studies; n = 2606 participants), or neutralizing response (n = 7 studies; n = 1123 participants), we did not find strong evidence to support any difference in serological markers between groups with and without persisting symptoms. However, most studies did not account for severity or level of care required during acute illness, and other potential confounders.

CONCLUSIONS

Pooling of studies would enable more robust exploration of clinical and serological predictors among diverse populations. However, substantial inter-study variations hamper comparability. Standardized reporting practices would improve the quality, consistency and comprehension of study findings.

Short- and Long-Term Chest-CT Findings after Recovery from COVID-19: A Systematic Review and Meta-Analysis

While ground-glass opacity, consolidation, and fibrosis in the lungs are some of the hallmarks of acute SAR-CoV-2 infection, it remains unclear whether these pulmonary radiological findings would resolve after acute symptoms have subsided. We conducted a systematic review and meta-analysis to evaluate chest computed tomography (CT) abnormalities stratified by COVID-19 disease severity and multiple timepoints post-infection. PubMed/MEDLINE was searched for relevant articles until 23 May 2023. Studies with COVID-19-recovered patients and follow-up chest CT at least 12 months post-infection were included. CT findings were evaluated at short-term (1-6 months) and long-term (12-24 months) follow-ups and by disease severity (severe and non-severe). A generalized linear mixed-effects model with random effects was used to estimate event rates for CT findings. A total of 2517 studies were identified, of which 43 met the inclusion (N = 8858 patients). Fibrotic-like changes had the highest event rate at short-term (0.44 [0.3-0.59]) and long-term (0.38 [0.23-0.56]) follow-ups. A meta-regression showed that over time the event rates decreased for any abnormality (β = -0.137, p = 0.002), ground-glass opacities (β = -0.169, p < 0.001), increased for honeycombing (β = 0.075, p = 0.03), and did not change for fibrotic-like changes, bronchiectasis, reticulation, and interlobular septal thickening (p > 0.05 for all). The severe subgroup had significantly higher rates of any abnormalities (p < 0.001), bronchiectasis (p = 0.02), fibrotic-like changes (p = 0.03), and reticulation (p < 0.001) at long-term follow-ups when compared to the non-severe subgroup. In conclusion, significant CT abnormalities remained up to 2 years post-COVID-19, especially in patients with severe disease. Long-lasting pulmonary abnormalities post-SARS-CoV-2 infection signal a future public health concern, necessitating extended monitoring, rehabilitation, survivor support, vaccination, and ongoing research for targeted therapies.

An immune signature of postoperative cognitive decline in elderly patients

Postoperative cognitive decline (POCD) is the predominant complication affecting elderly patients following major surgery, yet its prediction and prevention remain challenging. Understanding biological processes underlying the pathogenesis of POCD is essential for identifying mechanistic biomarkers to advance diagnostics and therapeutics. This longitudinal study involving 26 elderly patients undergoing orthopedic surgery aimed to characterize the impact of peripheral immune cell responses to surgical trauma on POCD. Trajectory analyses of single-cell mass cytometry data highlighted early JAK/STAT signaling exacerbation and diminished MyD88 signaling post-surgery in patients who developed POCD. Further analyses integrating single-cell and plasma proteomic data collected before surgery with clinical variables yielded a sparse predictive model that accurately identified patients who would develop POCD (AUC = 0.80). The resulting POCD immune signature included one plasma protein and ten immune cell features, offering a concise list of biomarker candidates for developing point-of-care prognostic tests to personalize perioperative management of at-risk patients. The code and the data are documented and available at https://github.com/gregbellan/POCD .

Teaser

Modeling immune cell responses and plasma proteomic data predicts postoperative cognitive decline.

SARS-CoV-2 seroprevalence and associated factors of infection before and after the Delta wave in French Polynesia: a cross-sectional study

BACKGROUND

French Polynesia (FP) comprises 75 inhabited islands scattered across five archipelagos. Between July and October 2021, the SARS-CoV-2 Delta variant triggered a much stronger second epidemic wave in FP than the original Wuhan strain, which was dominant from August 2020 to March 2021. Although previous seroprevalence surveys made it possible to determine the proportion of the population infected by SARS-CoV-2 on the two most populated islands (Tahiti and Moorea) after the first (20.6% in Tahiti and 9.4% in Moorea) and second (57.7% in Tahiti) epidemic waves, no data are available for more remote islands. We used blood samples and personal data collected before, during, and after the second wave from inhabitants of several islands within the five archipelagos to assess the prevalence of SARS-CoV-2 infections and identify associated factors.

METHODS

Blood samples and personal data were collected between April and December 2021 as part of the MATAEA study, a cross-sectional survey conducted on a random sample of the adult population representative of the five FP archipelagos and stratified by age and gender. IgG antibodies targeting the SARS-CoV-2 nucleocapsid (N) protein were detected using a recombinant antigen-based microsphere immunoassay. Factors associated with anti-SARS-CoV-2-N seropositivity were identified using logistic regression models.

RESULTS

Of 1,120 participants, 503 (44.9%) tested positive for anti-SARS-CoV-2-N antibodies, corresponding to a weighted prevalence of 56.8% for the FP population aged 18-69 years. The seroprevalence increased from 21.9% to 62.1% before and during/after the Delta wave. Of these infections, only 28.4% had been diagnosed by health professionals. The odds of being seropositive were lower in males, participants recruited before the Delta wave, those who had never been married, those with a diagnosed respiratory allergy, smokers, and those vaccinated against COVID-19.

CONCLUSIONS

Our results confirm the high impact of the Delta wave in FP. By the end of 2021, 56.8% of the FP population aged 18-69 years had been infected by SARS-CoV-2; the majority of these infections went undetected. Individuals with respiratory allergies were found to be less susceptible to SARS-CoV-2 infection.

ER and SOCE Ca2+ signals are not required for directed cell migration in human microglia

The central nervous system (CNS) is constantly surveilled by microglia, highly motile and dynamic cells deputed to act as the first line of immune defense in the brain and spinal cord. Alterations in the homeostasis of the CNS are detected by microglia that respond by migrating toward the affected area. Understanding the mechanisms controlling directed cell migration of microglia is crucial to dissect their responses to neuroinflammation and injury. We used a combination of pharmacological and genetic approaches to explore the involvement of calcium (Ca2+) signaling in the directed migration of induced pluripotent stem cell (iPSC)-derived microglia challenged with a purinergic stimulus. This approach mimics cues originating from injury of the CNS. Unexpectedly, simultaneous imaging of microglia migration and intracellular Ca2+ changes revealed that this phenomenon does not require Ca2+ signals generated from the endoplasmic reticulum (ER) and store-operated Ca2+ entry (SOCE) pathways. Instead, we find evidence that human microglial chemotaxis to purinergic signals is mediated by cyclic AMP in a Ca2+-independent manner. These results challenge prevailing notions, with important implications in neurological conditions characterized by perturbation in Ca2+ homeostasis.

Innate Immune Activation and Mitochondrial ROS Invoke Persistent Cardiac Conduction System Dysfunction after COVID-19

Background

Cardiac risk rises during acute SARS-CoV-2 infection and in long COVID syndrome in humans, but the mechanisms behind COVID-19-linked arrhythmias are unknown. This study explores the acute and long term effects of SARS-CoV-2 on the cardiac conduction system (CCS) in a hamster model of COVID-19.

Methods

Radiotelemetry in conscious animals was used to non-invasively record electrocardiograms and subpleural pressures after intranasal SARS-CoV-2 infection. Cardiac cytokines, interferon-stimulated gene expression, and macrophage infiltration of the CCS, were assessed at 4 days and 4 weeks post-infection. A double-stranded RNA mimetic, polyinosinic:polycytidylic acid (PIC), was used in vivo and in vitro to activate viral pattern recognition receptors in the absence of SARS-CoV-2 infection.

Results

COVID-19 induced pronounced tachypnea and severe cardiac conduction system (CCS) dysfunction, spanning from bradycardia to persistent atrioventricular block, although no viral protein expression was detected in the heart. Arrhythmias developed rapidly, partially reversed, and then redeveloped after the pulmonary infection was resolved, indicating persistent CCS injury. Increased cardiac cytokines, interferon-stimulated gene expression, and macrophage remodeling in the CCS accompanied the electrophysiological abnormalities. Interestingly, the arrhythmia phenotype was reproduced by cardiac injection of PIC in the absence of virus, indicating that innate immune activation was sufficient to drive the response. PIC also strongly induced cytokine secretion and robust interferon signaling in hearts, human iPSC-derived cardiomyocytes (hiPSC-CMs), and engineered heart tissues, accompanied by alterations in electrical and Ca 2+ handling properties. Importantly, the pulmonary and cardiac effects of COVID-19 were blunted by in vivo inhibition of JAK/STAT signaling or by a mitochondrially-targeted antioxidant.

Conclusions

The findings indicate that long term dysfunction and immune cell remodeling of the CCS is induced by COVID-19, arising indirectly from oxidative stress and excessive activation of cardiac innate immune responses during infection, with implications for long COVID Syndrome.

JAK inhibitors for inflammatory bowel disease: recent advances

Inflammatory bowel disease (IBD) commonly requires immunosuppressive treatments to induce and maintain durable remission. Janus kinase inhibitors (JAKis) are a novel group of orally administered, small molecule drugs that work by attenuating multiple cytokine signalling pathways to mediate dysregulated immune responses involved in the pathogenesis of IBD. Tofacitinib, filgotinib and upadacitinib have demonstrated efficacy against placebo and are licensed for the treatment of moderate to severe ulcerative colitis; upadacitinib is the only JAKi also currently approved for the treatment of Crohn's disease. Safety concerns stratified by age have led to class-wide regulatory restrictions for JAKi use across all inflammatory diseases. It is important for gastroenterologists managing patients with IBD to be aware of the key pivotal trial outcomes, to identify appropriate patients in whom to commence a JAKi, and to understand the safety considerations and ways to mitigate these risks in the patients they treat. This review provides a contemporaneous overview of this emerging therapeutic class and provides a practical guide for healthcare practitioners for initiating and monitoring JAKi in IBD.

Systematic Review of the Prevalence of Long COVID

Background

Long COVID occurs in those infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) whose symptoms persist or develop beyond the acute phase. We conducted a systematic review to determine the prevalence of persistent symptoms, functional disability, or pathological changes in adults or children at least 12 weeks postinfection.

Methods

We searched key registers and databases from January 1, 2020 to November 2, 2021, limited to publications in English and studies with at least 100 participants. Studies in which all participants were critically ill were excluded. Long COVID was extracted as prevalence of at least 1 symptom or pathology, or prevalence of the most common symptom or pathology, at 12 weeks or later. Heterogeneity was quantified in absolute terms and as a proportion of total variation and explored across predefined subgroups (PROSPERO ID CRD42020218351).

Results

One hundred twenty studies in 130 publications were included. Length of follow-up varied between 12 weeks and 12 months. Few studies had low risk of bias. All complete and subgroup analyses except 1 had I² ≥90%, with prevalence of persistent symptoms range of 0%-93% (pooled estimate [PE], 42.1%; 95% prediction interval [PI], 6.8% to 87.9%). Studies using routine healthcare records tended to report lower prevalence (PE, 13.6%; PI, 1.2% to 68%) of persistent symptoms/pathology than self-report (PE, 43.9%; PI, 8.2% to 87.2%). However, studies systematically investigating pathology in all participants at follow up tended to report the highest estimates of all 3 (PE, 51.7%; PI, 12.3% to 89.1%). Studies of hospitalized cases had generally higher estimates than community-based studies.

Conclusions

The way in which Long COVID is defined and measured affects prevalence estimation. Given the widespread nature of SARS-CoV-2 infection globally, the burden of chronic illness is likely to be substantial even using the most conservative estimates.

Long-term evaluation of the seroprevalence of SARS-CoV-2 IgG and IgM antibodies in recovered patients: a meta-analysis

Estimating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) -specific immunoglobulin G (IgG) immunoglobulin M (IgM) antibodies are increasingly important for tracking the spread of infection and defining herd immunity barrier and individual immunization levels in the ongoing coronavirus disease 2019 (COVID-19) pandemic. Therefore, we conducted the present systematic review and meta-analysis to evaluate the seroprevalence of SARS-CoV-2 IgM and IgG antibodies of recovered COVID-19 patients in long-term follow-up studies. A systematic search of the MEDLINE, Embase, COVID-19 Primer, PubMed, CNKI, and the Public Health England library databases was conducted. Twenty-fourth eligible studies were included. Meta-analysis showed that 27% (95%CI: 0.04-0.49) and 66% (95%CI:0.47-0.85) were seropositive for SARS-CoV-2 IgM and IgG, respectively, while in long-term 12 months following up studies, the seroprevalences of IgM antibody (17%) decreased and IgG antibody (75%) was higher than 6 months follow-up patients. However, due to the limited number of relevant studies, the high level of heterogeneity, and the large gap in studies conducted, the findings of our study may not accurately reflect the true seroprevalence status of SARS-CoV-2 infection. Nevertheless, sequential vaccination or booster immunization is considered to be a necessary long-term strategy to sustain the fight against the pandemic.

Detection of Post-COVID-19 Lung Abnormalities: Photon-counting CT versus Same-Day Energy-integrating Detector CT

Background Photon-counting detector (PCD) CT enables ultra-high-resolution lung imaging and may shed light on morphologic correlates of persistent symptoms after COVID-19. Purpose To compare PCD CT with energy-integrating detector (EID) CT for noninvasive assessment of post-COVID-19 lung abnormalities. Materials and Methods For this prospective study, adult participants with one or more COVID-19-related persisting symptoms (resting or exertional dyspnea, cough, fatigue) underwent same-day EID and PCD CT between April 2022 and June 2022. The 1.0-mm EID CT images and, subsequently, 1.0-, 0.4-, and 0.2-mm PCD CT images were reviewed for the presence of lung abnormalities. Subjective and objective EID and PCD CT image quality were evaluated using a five-point Likert scale (-2 to 2) and lung signal-to-noise ratios (SNRs). Results Twenty participants (mean age, 54 years ± 16 [SD]; 10 men) were included. EID CT showed post-COVID-19 lung abnormalities in 15 of 20 (75%) participants, with a median involvement of 10% of lung volume [IQR, 0%-45%] and 3.5 lobes [IQR, 0-5]. Ground-glass opacities and linear bands (10 of 20 participants [50%] for both) were the most frequent findings at EID CT. PCD CT revealed additional lung abnormalities in 10 of 20 (50%) participants, with the most common being bronchiectasis (10 of 20 [50%]). Subjective image quality was improved for 1.0-mm PCD versus 1.0-mm EID CT images (median, 1; IQR, 1-2; P < .001) and 0.4-mm versus 1.0-mm PCD CT images (median, 1; IQR, 1-1; P < .001) but not for 0.4-mm versus 0.2-mm PCD CT images (median, 0; IQR, 0-0.5; P = .26). PCD CT delivered higher lung SNR versus EID CT for 1.0-mm images (mean difference, 0.53 ± 0.96; P = .03) but lower SNR for 0.4-mm versus 1.0-mm images and 0.2-mm vs 0.4-mm images (-1.52 ± 0.68 [P < .001] and -1.15 ± 0.43 [P < .001], respectively). Conclusion Photon-counting detector CT outperformed energy-integrating detector CT in the visualization of subtle post-COVID-19 lung abnormalities and image quality. © RSNA, 2023 Supplemental material is available for this article.

Pooled Prevalence of Long COVID-19 Symptoms at 12 Months and Above Follow-Up Period: A Systematic Review and Meta-Analysis

Current data suggests that coronavirus disease 2019 (COVID-19) survivors experience long-lasting problems. It is not yet understood how long these symptoms last. The goal of this study was to compile all the data that was currently available to evaluate COVID-19's long-term effects at 12 months and above. We looked for studies published by December 15, 2022, in PubMed and Embase that discussed follow-up findings for COVID-19 survivors who had been alive for at least a year. A random-effect model was carried out to determine the combined prevalence of different long-COVID symptoms. The Joanna Briggs Institute tool was used to assess the risk of bias for the included studies, and the I2 statistics were used to evaluate the heterogeneity. After reviewing 3,209 studies, 46 were deemed admissible, with an aggregate COVID-19 population of 17976. At 12 months and above, 57% of patients reported a minimum of one symptom, and the five most prevalent symptoms were: dyspnea on exertion (34%, 95% CI 0.2; 0.94); difficulty in concentration (32%, 95% CI 0.16; 0.52); fatigue (31%, 95% CI 0.22; 0.40); frailty (31%, 95% CI 0.06; 0.78); and arthromyalgia (28%, 95% CI 0.09; 0.6). The findings of the present study showed that at 12 months and beyond, a sizable fraction of COVID-19 survivors still have lasting symptoms that impair several body systems. Long-COVID patients require an urgent understanding of pathophysiological processes and the development of tailored treatments.

Trajectories of Seroprevalence and Neutralizing Activity of Antibodies against SARS-CoV-2 in Southern Switzerland between July 2020 and July 2021: An Ongoing, Prospective Population-Based Cohort Study

OBJECTIVES

The COVID-19 pandemic continues, and evidence on infection- and vaccine-induced immunity is key. We assessed COVID-19 immunity and the neutralizing antibody response to virus variants across age groups in the Swiss population.

STUDY DESIGN

We conducted a cohort study in representative community-dwelling residents aged five years or older in southern Switzerland (total population 353,343), and we collected blood samples in July 2020 (in adults only, N = 646), November-December 2020 (N = 1457), and June-July 2021 (N = 885).

METHODS

We used a previously validated Luminex assay to measure antibodies targeting the spike (S) and the nucleocapsid (N) proteins of the virus and a high-throughput cell-free neutralization assay optimized for multiple spike protein variants. We calculated seroprevalence with a Bayesian logistic regression model accounting for the population's sociodemographic structure and the test performance, and we compared the neutralizing activity between vaccinated and convalescent participants across virus variants.

RESULTS

The overall seroprevalence was 7.8% (95% CI: 5.4-10.4) by July 2020 and 20.2% (16.4-24.4) by December 2020. By July 2021, the overall seroprevalence increased substantially to 72.5% (69.1-76.4), with the highest estimates of 95.6% (92.8-97.8) among older adults, who developed up to 10.3 more antibodies via vaccination than after infection compared to 3.7 times more in adults. The neutralizing activity was significantly higher for vaccine-induced than infection-induced antibodies for all virus variants (all p values < 0.037).

CONCLUSIONS

Vaccination chiefly contributed to the reduction in immunonaive individuals, particularly those in older age groups. Our findings on the greater neutralizing activity of vaccine-induced antibodies than infection-induced antibodies are greatly informative for future vaccination campaigns.

Role of T cells in severe COVID-19 disease, protection, and long term immunity

Infection with SARS-CoV-2 causes wide range of disease severities from asymptomatic to life-threatening disease. Understanding the contribution of immunological traits in immunity against SARS-CoV-2 and in protection against severe COVID-19 could result in effective measures to prevent development of severe disease. While the role of cytokines and antibodies has been thoroughly studied, this is not the case for T cells. In this review, the association between T cells and COVID-19 disease severity and protection upon reexposure is discussed. While infiltration of overactivated cytotoxic T cells might be harmful in the infected tissue, fast responding T cells are important in the protection against severe COVID-19. This protection could even be viable in the long term as long-living memory T cells seem to be stabilized and mutations do not appear to have a large impact on T cell responses. Thus, after vaccination and infections, memory T cells should be able to help prevent onset of severe disease for most cases. Considering this, it would be useful to add N or M proteins in vaccinations, alongside the S protein which is currently used, as this results in a broader T cell response.

Predictors of pulmonary sequelae after COVID-19 pneumonia: A 12-month follow-up study

Background

Since the beginning of the SARS-CoV-2 pandemic, over 550 million people have been infected worldwide. Despite these large numbers, the long-term pulmonary consequences of COVID-19 remain unclear.

Aims

The aim of this single-center observational cohort study was to identify and characterize pulmonary sequelae of COVID-19 at 12 months from hospitalization and to reveal possible predictors for the persistence of long-term lung consequences.

Methods

Based on the persistence or absence of radiological changes after 12 months from hospitalization, the whole population was categorized into NOT-RECOVERED (NOT-REC) and RECOVERED (REC) groups, respectively. Clinical and pulmonary function data tests and clinical data were also collected and compared in the two groups. In the NOT-REC group, high resolution computed tomography (HRCT) images were semiquantitatively scored analyzing ground-glass opacities (GGO), interstitial thickening (IT), consolidations (CO), linear and curvilinear band opacities, and bronchiectasis for each lung lobe. Logistic regression analyses served to detect the factors associated with 12-month radiological consequences.

Results

Out of the 421 patients followed after hospitalization for SARS-CoV-2 pneumonia, 347 met inclusion and exclusion criteria and were enrolled in the study. The NOT-REC patients (n = 24; 6.9%) were significantly older [67 (62-76) years vs. 63 (53-71) years; p = 0.02], more frequently current smokers [4 (17%) vs. 12 (4%); p = 0.02], and with more severe respiratory failure at the time of hospitalization [PaO₂/FiO₂ at admission: 201 (101-314) vs. 295 (223-343); p = 0.01] compared to REC group (n = 323; 93.1%). On multivariable analysis, being a current smoker resulted in an independent predictor for lung sequelae after 12 months from hospitalization [5.6 OR; 95% CI (1.41-22.12); p = 0.01].

Conclusion

After 12 months from hospital admission, a limited number of patients displayed persistent pulmonary sequelae with minimal extension. Being a current smoker at the time of SARS-CoV-2 infection is an independent predictive factor to lung consequences, regardless of the disease severity.

Cardiovascular Disease in Post-Acute COVID-19 Syndrome: A Comprehensive Review of Pathophysiology and Diagnosis Approach

Long COVID or post-acute Coronavirus disease 2019 (COVID-19), a malady defined by the persistence of COVID-19 symptoms for weeks or even months, is expected to affect the lives of millions of individuals worldwide significantly. Cardiopulmonary symptoms such as chest discomfort, shortness of breath, fatigue, and autonomic manifestations such as postural orthostatic tachycardia syndrome, and arrhythmias are prevalent and widely recognized. A variety of cardiovascular problems, including myocardial inflammation, myocardial infarction, ventricular dysfunction, and endothelial dysfunction, have been described in individuals following the initial acute phase. With over 10,000 published publications on COVID-19 and the cardiovascular system, presenting an unbiased thorough analysis of how SARS-CoV-2 affects the system is essentially challenging. This review will provide an overview of frequent cardiovascular manifestations, emphasizing consequences, proposed pathophysiology, and clinical diagnostic manifestation strategy.

Statistical biases due to anonymization evaluated in an open clinical dataset from COVID-19 patients

Anonymization has the potential to foster the sharing of medical data. State-of-the-art methods use mathematical models to modify data to reduce privacy risks. However, the degree of protection must be balanced against the impact on statistical properties. We studied an extreme case of this trade-off: the statistical validity of an open medical dataset based on the German National Pandemic Cohort Network (NAPKON), which was prepared for publication using a strong anonymization procedure. Descriptive statistics and results of regression analyses were compared before and after anonymization of multiple variants of the original dataset. Despite significant differences in value distributions, the statistical bias was found to be small in all cases. In the regression analyses, the median absolute deviations of the estimated adjusted odds ratios for different sample sizes ranged from 0.01 [minimum = 0, maximum = 0.58] to 0.52 [minimum = 0.25, maximum = 0.91]. Disproportionate impact on the statistical properties of data is a common argument against the use of anonymization. Our analysis demonstrates that anonymization can actually preserve validity of statistical results in relatively low-dimensional data.

Cardiac Manifestations of Post-Acute COVID-19 Infection

PURPOSE OF REVIEW

There is emerging evidence that the post-acute and chronic phases of COVID-19 infection are associated with various significant cardiovascular sequelae.

RECENT FINDINGS

Long COVID has been shown to be associated with multiple cardiovascular sequelae including direct myocardial injury, arrhythmias, and cardiomyopathies. Hypotheses on the mechanism of myocardial injury include direct viral infiltration and autoimmune dysregulation. Long COVID is associated with persistent cardiac ischemia in patients with no previous history of coronary disease, atrial and ventricular arrhythmias, and the development of new-onset heart failure in previously healthy patients. Onset of long COVID may be related to severity of the initial SARS-CoV2 infection. Cardiac MRI is a valuable tool in assessing myocarditis and the development of cardiomyopathies in the setting of long COVID. Both patients with and without pre-existing cardiovascular disease are at risk of developing myocardial injury in the setting of long COVID. Future studies will elucidate both cardiovascular mortality and cardiac rehabilitation in the post-acute and chronic phases of COVID-19.

Detection of Post-COVID-19 Lung Abnormalities: Photon-counting CT versus Same-day Energy-integrating Detector CT

Background Photon-counting detector (PCD) CT allows ultra-high-resolution lung imaging and may shed light on morphologic correlates of persistent symptoms after COVID-19. Purpose To compare PCD CT with energy-integrating detector (EID) CT for noninvasive assessment of post-COVID-19 lung abnormalities. Materials and Methods For this prospective study, adult participants with one or more COVID-19-related persisting symptoms (resting or exertional dyspnea, cough, and fatigue) underwent same-day EID and PCD CT scans between April 2022 and June 2022. EID CT 1.0mm images and, subsequently, 1.0mm, 0.4mm, and 0.2mm PCD CT images were reviewed for the presence of lung abnormalities. Subjective and objective EID and PCD CT image quality was evaluated using a 5-point Likert scale (-2 to 2) and lung signal-to-noise ratios (SNR). Results Twenty participants (mean age, 54 years ±16 [SD], 10 men) were included. EID CT showed post-COVID-19 lung abnormalities in 15 of 20 (75%) participants with a median involvement of 10% of lung volume [IQR 0-45%], and 3.5 lobes [IQR 0-5]. Ground-glass opacities (GGO) and linear bands (both 10 of 20 participants, 50%) were the most frequent findings on EID CT. PCD CT revealed additional lung abnormalities in 10 of 20 (50%) participants, most commonly bronchiolectasis (10 of 20, 50%). Subjective image quality was improved for 1.0mm PCD vs. 1.0mm EID CT images (1 [IQR 1-2], P<.001) and 0.4mm vs. 1.0mm PCD CT images (1 [IQR 1-1], P<.001), but not for 0.4mm vs. 0.2mm PCD CT images (0 [IQR 0-0.5], P=.26). PCD CT delivered higher lung SNR vs. EID CT 1.0mm images (mean difference 0.53 ± 0.96, P=.03), but lower SNRs for 0.4mm vs. 1.0mm images, and 0.2mm vs. 0.4mm images, respectively (-1.52 ± 0.68, P<.001 and -1.15 ± 0.43, P<.001). Conclusion Photon-counting detector CT outperformed energy-integrating detector CT with regard to visualization of subtle post-COVID-19 lung abnormalities and image quality.

The Comparative Superiority of SARS-CoV-2 Antibody Response in Different Immunization Scenarios

Background: Both SARS-CoV-2 infection and/or vaccination result in the production of SARS-CoV-2 antibodies. We aimed to compare the antibody titers against SARS-CoV-2 in different scenarios for antibody production. Methods: A surveillance program was conducted in the municipality of Deskati in January 2022. Antibody titers were obtained from 145 participants while parallel recording their infection and/or vaccination history. The SARS-CoV-2 IgG II Quant method (Architect, Abbott, IL, USA) was used for antibody testing. Results: Advanced age (>56 years old) was associated with higher antibody titers. No significant differences were detected in antibody titers among genders, BMI, smoking status, comorbidities, vaccine brands, and months after the last dose. Hospitalization length and re-infection were predictors of antibody titers. The individuals who were fully or partially vaccinated and were also double infected had the highest antibody levels (25,017 ± 1500 AU/mL), followed by people who were fully vaccinated (20,647 ± 500 AU/mL) or/partially (15,808 ± 1800 AU/mL) vaccinated and were infected once. People who were only vaccinated had lower levels of antibodies (9946 ± 300 AU/mL), while the lowest levels among all groups were found in individuals who had only been infected (1124 ± 200 AU/mL). Conclusions: Every hit (infection or vaccination) gives an additional boost to immunization status.

Long-term Lung Abnormalities Associated with COVID-19 Pneumonia

In the 3rd year of the SARS-CoV-2 pandemic, much has been learned about the long-term effects of COVID-19 pneumonia on the lungs. Approximately one-third of patients with moderate-to-severe pneumonia, especially those requiring intensive care therapy or mechanical ventilation, have residual abnormalities at chest CT 1 year after presentation. Abnormalities range from parenchymal bands to bronchial dilation to frank fibrosis. Less is known about the long-term pulmonary vascular sequelae, but there appears to be a persistent, increased risk of venothromboembolic events in a small cohort of patients. Finally, the associated histologic abnormalities resulting from SARS-CoV-2 infection are similar to those seen in patients with other causes of acute lung injury.

Kinetics of severe acute respiratory syndrome coronavirus 2 infection antibody responses

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly throughout the world, causing severe morbidity and mortality. Since the first reports of Coronavirus disease 2019 (COVID-19) in late 2019, research on the characteristics of specific humoral immunity against SARS-CoV-2 in patients with COVID-19 has made great progress. However, our knowledge of persistent humoral immunity to SARS-CoV-2 infection is limited. The existence of protective immunity after infection will affect future transmission and disease severity. Therefore, it is important to gather knowledge about the kinetics of antibody responses. In this review, we summarize the information obtained so far on the characteristics and kinetics of the SARS-CoV-2 infection of specific humoral immune response, especially in neutralizing antibodies and their relationship with disease severity. In addition, with the emergence of variants of concern, we summarize the neutralizing effect of specific humoral immunity on variants of concern after the initial SARS-CoV-2 infection and vaccination.

One-year follow-up study after patients with severe COVID-19 received human umbilical cord mesenchymal stem cells treatment

Background

The novel coronavirus is still mutating, and the pandemic continues. Meanwhile, many COVID-19 survivors have residual postinfection clinical manifestations. Human umbilical cord mesenchymal stem cells (hUC-MSCs) have been shown to be effective in the early stages of COVID-19.

Objectives

The aim of this study was to investigate long-term safety and efficacy of treatment in patients with severe COVID-19 patients who had received hUC-MSCs therapy.

Methods

Twenty-five discharged patients who had severe COVID-19 (including the standard treatment group and the standard treatment plus hUC-MSCs group) were enrolled in a 1-year follow-up. The assessment considered adverse effects (including effects on liver and kidney function, coagulation, ECG, tumor marker, and so on), pulmonary function, St George’s Respiratory Questionnaire (SGRQ), postinfection sequelae and serum concentration of Krebs von den Lungen-6 (KL-6), malondialdehyde (MDA), H₂S, carnitine, and N-6 long-chain polyunsaturated fatty acids (N-6 LC-PUFAs).

Measurements and main results

Pulmonary ventilation function had significantly improved at the 1-year follow-up in both the hUC-MSCs group and the control group compared with the 3-month follow-up (P < 0.01). Fatigue (60% [15/25]) remained the most common symptom at the 1-year follow-up. The rate of fatigue relief was significantly reduced in the hUC-MSCs group (25% [2/8]) compared to the control group (76.5% [13/17]) (P = 0.028). The level of KL-6 was significantly lower in the hUC-MSCs group (2585.5 ± 186.5 U/ml) than in the control group (3120.7 ± 158.3 U/ml) (P < 0.001). Compared with the control group, the hUC-MSCs group had a lower level of MDA (9.27 ± 0.54 vs. 9.91 ± 0.72 nmol/ml, P = 0.036). No obvious adverse effects were observed in the hUC-MSCs treatment group at 1 year after discharge.

Conclusions

Intravenous transplantation of hUC-MSCs was a safe approach in the long term in the treatment of patients with severe COVID-19. In addition, hUC-MSCs had a positive effect on postinfection sequelae in COVID-19 survivors.

Trial registration

Chinese Clinical Trial Registration; ChiCTR2000031494; Registered 02 April 2020—Retrospectively registered, http://www.medresman.org

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02972-3.

One-year follow-up CT findings in COVID-19 patients: A systematic review and meta-analysis

Coronavirus disease 2019 (COVID‐19) often causes radiological and functional pulmonary sequelae. However, evidence on 1‐year follow‐up of pulmonary sequelae is limited. We aimed to investigate the characteristics and time‐course of pulmonary sequelae after recovery from COVID‐19 through 1‐year follow‐up. We searched PubMed and EMBASE databases on 25 February 2022, and included studies with computed tomography (CT) findings at the 1‐year follow‐up. The extracted data on CT findings were analysed using a one‐group meta‐analysis. We further analysed the data in relation to COVID‐19 severity, improvement rate and lung function. Fifteen eligible studies (N = 3134) were included. One year after COVID‐19, 32.6% (95% CI 24.0–42.6, I² = 92.9%) presented with residual CT abnormalities. Ground‐glass opacity and fibrotic‐like changes were frequently observed in 21.2% (95% CI 15.4–28.4, I² = 86.7%) and 20.6% (95% CI 11.0–35.2, I² = 91.9%), respectively. While the gradual recovery was seen on CT (52.9% [mid‐term] vs. 32.6% [1 year]), the frequency of CT abnormalities was higher in the severe/critical cases than in the mild/moderate cases (37.7% vs. 20.7%). In particular, fibrotic changes showed little improvement between 4–7 months and 1 year after COVID‐19. Pulmonary function tests at 1 year also showed the decline in diffusing capacity of the lung for carbon monoxide, especially in severe/critical cases. Our meta‐analysis indicated that residual CT abnormalities were common in hospitalized COVID‐19 patients 1 year after recovery, especially fibrotic changes in severe/critical cases. As these sequelae may last long, vigilant observations and longer follow‐up periods are warranted.

Long-Term Consequences of COVID-19 at 6 Months and Above: A Systematic Review and Meta-Analysis

We aimed to review the data available to evaluate the long-term consequences of coronavirus disease 2019 (COVID-19) at 6 months and above. We searched relevant observational cohort studies up to 9 February 2022 in Pubmed, Embase, and Web of Science. Random-effects inverse-variance models were used to evaluate the Pooled Prevalence (PP) and its 95% confidence interval (CI) of long-term consequences. The Newcastle−Ottawa quality assessment scale was used to assess the quality of the included cohort studies. A total of 40 studies involving 10,945 cases of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection were included. Of the patients, 63.87% had at least one consequence at the 6 month follow-up, which decreased to 58.89% at 12 months. The most common symptoms were fatigue or muscle weakness (PP 6−12 m = 54.21%, PP ≥ 12 m = 34.22%) and mild dyspnea (Modified Medical Research Council Dyspnea Scale, mMRC = 0, PP 6−12 m = 74.60%, PP ≥ 12 m = 80.64%). Abnormal computerized tomography (CT; PP 6−12 m = 55.68%, PP ≥ 12 m = 43.76%) and lung diffuse function impairment, i.e., a carbon monoxide diffusing capacity (DLCO) of < 80% were common (PP 6−12 m = 49.10%, PP ≥ 12 m = 31.80%). Anxiety and depression (PP 6−12 m = 33.49%, PP ≥ 12 m = 35.40%) and pain or discomfort (PP 6−12 m = 33.26%, PP ≥ 12 m = 35.31%) were the most common problems that affected patients’ quality of life. Our findings suggest a significant long-term impact on health and quality of life due to COVID-19, and as waves of ASRS-CoV-2 infections emerge, the long-term effects of COVID-19 will not only increase the difficulty of care for COVID-19 survivors and the setting of public health policy but also might lead to another public health crisis following the current pandemic, which would also increase the global long-term burden of disease.

Projecting the Pandemic Trajectory through Modeling the Transmission Dynamics of COVID-19

The course of the COVID-19 pandemic has given rise to many disease trends at various population scales, ranging from local to global. Understanding these trends and the epidemiological phenomena that lead to the changing dynamics associated with disease progression is critical for public health officials and the global community to rein in further spread of this and other virulent diseases. Classic epidemiological modeling based on dynamical systems are powerful tools used for modeling and understanding diseases, but often necessitate modifications to the classic compartmental models to reflect empirical observations. In this paper, we present a collection of extensions to the classic SIRS model to support public health decisions associated with viral pandemics. Specifically, we present models that reflect different levels of disease severity among infected individuals, capture the effect of vaccination on different population groups, capture the effect of different vaccines with different levels of effectiveness, and model the impact of a vaccine with varying number of doses. Further, our mathematical models support the investigation of a pandemic's trend under the emergence of new variants and the associated reduction in vaccine effectiveness. Our models are supported through numerical simulations, which we use to illustrate phenomena that have been observed in the COVID-19 pandemic. Our findings also confirm observations that the mild infectious group accounts for the majority of infected individuals, and that prompt immunization results in weaker pandemic waves across all levels of infection as well as a lower number of disease-caused deaths. Finally, using our models, we demonstrate that, when dealing with a single variant and having access to a highly effective vaccine, a three-dose vaccine has a strong ability to reduce the infectious population. However, when a new variant with higher transmissibility and lower vaccine efficiency emerges, it becomes the dominant circulating variant, as was observed in the recent emergence of the Omicron variant.

Qingjin Yiqi granules for post-COVID-19 condition: A randomized clinical trial

OBJECTIVE

To evaluate the effectiveness and safety of Qingjin Yiqi granules (QJYQ) on post-COVID-19 condition (PCC).

METHOD

Patients who met the inclusion criteria were randomly assigned to two groups, the QJYQ group received QJYQ combined with standard rehabilitation treatments (SRTs) and the control group only received SRTs. The treatment course was 14 days. The primary outcomes were modified Medical Research Council (mMRC) scale and Borg scale, while the secondary outcomes included symptoms score and 6-minute walking distance (6MWD). The safety outcome was the incidence of adverse events.

RESULTS

A total of 388 patients with PCC were enrolled and randomly assigned to the QJYQ group (n = 194) and the control group (n = 194). Compared to the controls, the mMRC scale was improved in the QJYQ group, which was better than that of the control group [β (95%CI): -0.626 (-1.101, -0.151), p = 0.010]. A significant improvement in Borg scale was also observed in the QJYQ group compared to the control group [β (95%CI): -0.395(-0.744, -0.046), p = 0.026]. There was no statistically significant difference in symptoms score and 6MWD between the two groups (p = 0.293, p = 0.724). No treatment-related adverse events were observed in either group.

CONCLUSIONS

QJYQ can bring benefits to patients with PCC, mainly in the improvement of breathlessness and fatigue.

Long-Term Sequelae of COVID-19: A Systematic Review and Meta-Analysis of One-Year Follow-Up Studies on Post-COVID Symptoms

Emerging evidence has shown that COVID-19 survivors could suffer from persistent symptoms. However, it remains unclear whether these symptoms persist over the longer term. This study aimed to systematically synthesise evidence on post-COVID symptoms persisting for at least 12 months. We searched PubMed and Embase for papers reporting at least one-year follow-up results of COVID-19 survivors published by 6 November 2021. Random-effects meta-analyses were conducted to estimate pooled prevalence of specific post-COVID symptoms. Eighteen papers that reported one-year follow-up data from 8591 COVID-19 survivors were included. Fatigue/weakness (28%, 95% CI: 18-39), dyspnoea (18%, 95% CI: 13-24), arthromyalgia (26%, 95% CI: 8-44), depression (23%, 95% CI: 12-34), anxiety (22%, 95% CI: 15-29), memory loss (19%, 95% CI: 7-31), concentration difficulties (18%, 95% CI: 2-35), and insomnia (12%, 95% CI: 7-17) were the most prevalent symptoms at one-year follow-up. Existing evidence suggested that female patients and those with more severe initial illness were more likely to suffer from the sequelae after one year. This study demonstrated that a sizeable proportion of COVID-19 survivors still experience residual symptoms involving various body systems one year later. There is an urgent need for elucidating the pathophysiologic mechanisms and developing and testing targeted interventions for long-COVID patients.

Single-Cell Analysis Reveals the Immune Characteristics of Myeloid Cells and Memory T Cells in Recovered COVID-19 Patients With Different Severities

Despite many studies on the immune characteristics of Coronavirus disease 2019 (COVID-19) patients in the progression stage, a detailed understanding of pertinent immune cells in recovered patients is lacking. We performed single-cell RNA sequencing on samples from recovered COVID-19 patients and healthy controls. We created a comprehensive immune landscape with more than 260,000 peripheral blood mononuclear cells (PBMCs) from 41 samples by integrating our dataset with previously reported datasets, which included samples collected between 27 and 47 days after symptom onset. According to our large-scale single-cell analysis, recovered patients, who had severe symptoms (severe/critical recovered), still exhibited peripheral immune disorders 1-2 months after symptom onset. Specifically, in these severe/critical recovered patients, human leukocyte antigen (HLA) class II and antigen processing pathways were downregulated in both CD14 monocytes and dendritic cells compared to healthy controls, while the proportion of CD14 monocytes increased. These may lead to the downregulation of T-cell differentiation pathways in memory T cells. However, in the mild/moderate recovered patients, the proportion of plasmacytoid dendritic cells increased compared to healthy controls, accompanied by the upregulation of HLA-DRA and HLA-DRB1 in both CD14 monocytes and dendritic cells. In addition, T-cell differentiation regulation and memory T cell-related genes FOS, JUN, CD69, CXCR4, and CD83 were upregulated in the mild/moderate recovered patients. Further, the immunoglobulin heavy chain V3-21 (IGHV3-21) gene segment was preferred in B-cell immune repertoires in severe/critical recovered patients. Collectively, we provide a large-scale single-cell atlas of the peripheral immune response in recovered COVID-19 patients.