Features of acute COVID-19 associated with post-acute sequelae of SARS-CoV-2 phenotypes: results from the IMPACC study

Distinct type 1 immune networks underlie the severity of restrictive lung disease after COVID-19

The variable origins of persistent breathlessness after coronavirus disease 2019 (COVID-19) have hindered efforts to decipher the immunopathology of lung sequelae. Here we analyzed hundreds of cellular and molecular features in the context of discrete pulmonary phenotypes to define the systemic immune landscape of post-COVID lung disease. Cluster analysis of lung physiology measures highlighted two phenotypes of restrictive lung disease that differed according to their impaired diffusion and severity of fibrosis. Machine learning revealed marked CCR5+CD95+CD8+ T cell perturbations in milder lung disease but attenuated T cell responses hallmarked by elevated CXCL13 in more severe disease. Distinct sets of cells, mediators and autoantibodies distinguished each restrictive phenotype and differed from those of patients without substantial lung involvement. These differences were reflected in divergent T cell-based type 1 networks according to the severity of lung disease. Our findings, which provide an immunological basis for active lung injury versus advanced disease after COVID-19, might offer new targets for treatment.

An Allele of the MTHFR one-carbon metabolism gene predicts severity of COVID-19

While the public health burden of SARS-CoV-2 infection has lessened due to natural and vaccine-acquired immunity, the emergence of less virulent variants, and antiviral medications, COVID-19 continues to take a significant toll. There are > 10,000 new hospitalizations per week in the U.S., many of whom develop post-acute sequelae of SARS-CoV-2 (PASC), or "long COVID", with long-term health issues and compromised quality of life. Early identification of individuals at high risk of severe COVID-19 is key for monitoring and supporting respiratory status and improving outcomes. Therefore, precision tools for early detection of patients at high risk of severe disease can reduce morbidity and mortality. Here we report an untargeted and longitudinal metabolomic study of plasma derived from adult patients with COVID-19. One-carbon metabolism, a pathway previously shown as critical for viral propagation and disease progression, and a potential target for COVID-19 treatment, scored strongly as differentially abundant in patients with severe COVID-19. A follow-up targeted metabolite profiling revealed that one arm of the one-carbon metabolism pathway, the methionine cycle, is a major driver of the metabolic profile associated with disease severity. The methionine cycle produces S-adenosylmethionine (SAM), the methyl group donor important for methylation of DNA, RNA, and proteins, and its high abundance was reported to correlate with disease severity. Further, genomic data from the profiled patients revealed a genetic contributor to methionine metabolism and identified the C677T allele of the MTHFR gene as a pre-existing predictor of disease trajectory - patients homozygous for the MTHFR C677T have higher incidence of experiencing severe disease. Our results raise the possibility that screening for the common genetic MTHFR variant may be an actionable approach to stratify risk of COVID severity and may inform novel precision COVID-19 treatment strategies.

Identification of a multi-omics factor predictive of long COVID in the IMPACC study

Following SARS-CoV-2 infection, ∼10-35% of COVID-19 patients experience long COVID (LC), in which often debilitating symptoms persist for at least three months. Elucidating the biologic underpinnings of LC could identify therapeutic opportunities. We utilized machine learning methods on biologic analytes and patient reported outcome surveys provided over 12 months after hospital discharge from >500 hospitalized COVID-19 patients in the IMPACC cohort to identify a multi-omics "recovery factor". IMPACC participants who experienced LC had lower recovery factor scores compared to participants without LC. Biologic characterization revealed increased levels of plasma proteins associated with inflammation, elevated transcriptional signatures of heme metabolism, and decreased androgenic steroids in LC patients. The recovery factor was also associated with altered circulating immune cell frequencies. Notably, recovery factor scores were predictive of LC occurrence in patients as early as hospital admission, irrespective of acute disease severity. Thus, the recovery factor identifies patients at risk of LC early after SARS-CoV-2 infection and reveals LC biomarkers and potential treatment targets.

Machine learning models predict long COVID outcomes based on baseline clinical and immunologic factors

The post-acute sequelae of SARS-CoV-2 (PASC), also known as long COVID, remain a significant health issue that is incompletely understood. Predicting which acutely infected individuals will go on to develop long COVID is challenging due to the lack of established biomarkers, clear disease mechanisms, or well-defined sub-phenotypes. Machine learning (ML) models offer the potential to address this by leveraging clinical data to enhance diagnostic precision. We utilized clinical data, including antibody titers and viral load measurements collected at the time of hospital admission, to predict the likelihood of acute COVID-19 progressing to long COVID. Our machine learning models achieved median AUROC values ranging from 0.64 to 0.66 and AUPRC values between 0.51 and 0.54, demonstrating their predictive capabilities. Feature importance analysis revealed that low antibody titers and high viral loads at hospital admission were the strongest predictors of long COVID outcomes. Comorbidities, including chronic respiratory, cardiac, and neurologic diseases, as well as female sex, were also identified as significant risk factors for long COVID. Our findings suggest that ML models have the potential to identify patients at risk for developing long COVID based on baseline clinical characteristics. These models can help guide early interventions, improving patient outcomes and mitigating the long-term public health impacts of SARS-CoV-2.

Targeting the SARS-CoV-2 reservoir in long COVID

There are no approved treatments for post-COVID-19 condition (also known as long COVID), a debilitating disease state following SARS-CoV-2 infection that is estimated to affect tens of millions of people. A growing body of evidence shows that SARS-CoV-2 can persist for months or years following COVID-19 in a subset of individuals, with this reservoir potentially driving long-COVID symptoms or sequelae. There is, therefore, an urgent need for clinical trials targeting persistent SARS-CoV-2, and several trials of antivirals or monoclonal antibodies for long COVID are underway. However, because mechanisms of SARS-CoV-2 persistence are not yet fully understood, such studies require important considerations related to the mechanism of action of candidate therapeutics, participant selection, duration of treatment, standardisation of reservoir-associated biomarkers and measurables, optimal outcome assessments, and potential combination approaches. In addition, patient subgroups might respond to some interventions or combinations of interventions, making post-hoc analyses crucial. Here, we outline these and other key considerations, with the goal of informing the design, implementation, and interpretation of trials in this rapidly growing field. Our recommendations are informed by knowledge gained from trials targeting the HIV reservoir, hepatitis C, and other RNA viruses, as well as precision oncology, which share many of the same hurdles facing long-COVID trials.

Relationship Between Acute SARS-CoV-2 Viral Clearance and Long COVID-19 (Long COVID) Symptoms: A Cohort Study

BACKGROUND

The relationship between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral dynamics during acute infection and the development of long coronavirus disease 2019 (COVID-19), or "long COVID," is largely unknown.

METHODS

Between October 2021 and February 2022, 7361 people not known to have COVID-19 self-collected nasal swab samples for SARS-CoV-2 reverse-transcription polymerase chain reaction testing every 24-48 hours for 10-14 days. Participants whose first known SARS-CoV-2 infection was detected were surveyed for long COVID in August 2023. Their slopes of viral clearance were modeled using linear mixed effects models with random slopes and intercepts, and the relative risk (RR) of long COVID based on viral slopes was calculated using a log binomial model, adjusted for age, symptoms, and variant. Sex-based interaction terms were also evaluated for significance.

RESULTS

A total of 172 participants were eligible for analyses, and 59 (34.3%) reported long COVID. The risk of long COVID with 3-4 symptoms (adjusted RR, 2.44 [95% confidence interval, .88-6.82]) and ≥5 symptoms (4.97 [1.90-13.0]) increased with each unit increase in slope of viral clearance. While the probability of long COVID increased with slowed viral clearance among women, the same relationship was not observed among men (interaction term: P = .02). Acute SARS-CoV-2 symptoms of abdominal pain (adjusted RR, 5.41 [95% confidence interval, 2.44-12.0]), nausea (3.01 [1.31-6.89]), and body aches (2.58 [1.26-5.30]) were most strongly associated with long COVID.

CONCLUSIONS

We observed that slower viral clearance rates during acute COVID-19 were associated with increased risk and more symptoms of long COVID . Early viral-host dynamics appear to be mechanistically linked to the development of long COVID.

Post-acute sequelae of COVID-19 3 to 12 months after infection: Delta vs Omicron

OBJECTIVES

Studies have shown temporal changes in post-acute sequelae of COVID-19 (PASC) prevalence for early SARS-CoV-2 variants, although often lacking controls. This prospective study assesses the prevalence of symptoms in Delta- and Omicron-infected cases up to 12 months compared with population controls.

METHODS

Adult participants filled out surveys every 3 months (T0-T12) between July 2021 and August 2023. Cases were recruited with a positive SARS-CoV-2 test during the Delta or Omicron domination. Population controls were randomly invited from the Dutch Personal Records Database. Participants indicated the presence of 13 PASC-associated symptoms, and severity scores of fatigue, cognitive impairment, dyspnea, and pain. PASC prevalence was defined as the excess prevalence of havingat least one PASC-associated symptom in cases compared with population controls.

RESULTS

PASC prevalence was 34.3% at T3 and decreased to 21.7% at T12 for Delta and decreased from 18.7% at T3 to 16.7% at T12 for Omicron. At T12, the difference between Delta and Omicron was not significant. Delta cases generally had higher excess symptom scores for fatigue, dyspnea, and cognitive impairment than Omicron.

CONCLUSIONS

In the first 9 months after infection, PASC prevalence was higher for Delta than Omicron, but the difference reduced over time and approximated after 12 months.

The immune-endocrine interplay in sex differential responses to viral infection and COVID-19

Men are at higher risk for developing severe COVID-19 than women, while women are at higher risk for developing post-acute sequelae of COVID-19 (PASC). This highlights the impact of sex differences on immune responses and clinical outcomes of acute COVID-19 or PASC. A dynamic immune-endocrine interface plays an important role in the development of effective immune responses impacting the control of viral infections. In this opinion article we discuss mechanisms underlying the transcriptional and epigenetic regulation of immune responses by sex hormones during viral infections. We propose that disruption of this delicate immune-endocrine interplay can result in worsened outcomes of viral disease. We also posit that insights into these immune mechanisms can propel the development of novel immunomodulatory interventions that leverage immune-endocrine pathways to treat viral infections.

Perceptions of prevalence and management of post-acute sequelae of SARS-CoV-2 (PASC) infection among healthcare workers in Kweneng District, Botswana: Report of a district-wide survey

Over 9.5 million confirmed cases of COVID-19 infection have been recorded in Africa. The syndrome of post-acute sequelae of SARS-CoV-2 infection (PASC) affects an estimated 32% to 87% of COVID patients globally. Data regarding prevalence and impact of PASC in Botswana are limited. This study used a cross-sectional survey design to query healthcare workers in Kweneng District, Botswana about perceived PASC prevalence, duration, symptoms, impact, and management strategies. The survey was disseminated to participants via pre-existing WhatsApp groups and paper copy. Descriptive statistics were used to analyse quantitative data, including demographic data. 72 respondents consented and completed the survey, from an estimated 650 staff meeting eligibility criteria; 63% were female and 36% were male. The majority (90%) were nurses, with doctors and "other" accounting for 6% and 4% of respondents, respectively; no administrators responded. Over half (72%) worked at primary care facilities and 28% worked in hospitals. Nearly all (93%) indicated seeing patients with PASC on a weekly basis, though the majority (61%) identified these patients as comprising <10% of total patients. The most frequently reported PASC symptom was persistent cough (64%), followed by shortness of breath (54%) and fatigue (49%). A substantial minority of respondents were unsure how to manage common PASC symptoms, with 29% and 36% indicating uncertainty regarding management of persistent cough and fatigue, respectively. Findings indicate that PASC symptoms are frequently encountered in clinical practice in Botswana with significant overlap with acute COVID-19, influenza-like illnesses, and tuberculosis, likely placing increased burden on existing health system processes. Providers reported uncertainty in managing presumed PASC, and current practice patterns may contribute to unintended adverse effects. Clear clinical algorithms for PASC screening, diagnosis, and management should be developed and disseminated in Botswana to mitigate the effects of PASC symptoms and improve the quality of life of COVID-19 survivors.

Unraveling SARS-CoV-2 Host-Response Heterogeneity through Longitudinal Molecular Subtyping

Hospitalized COVID-19 patients exhibit diverse immune responses during acute infection, which are associated with a wide range of clinical outcomes. However, understanding these immune heterogeneities and their links to various clinical complications, especially long COVID, remains a challenge. In this study, we performed unsupervised subtyping of longitudinal multi-omics immunophenotyping in over 1,000 hospitalized patients, identifying two critical subtypes linked to mortality or mechanical ventilation with prolonged hospital stay and three severe subtypes associated with timely acute recovery. We confirmed that unresolved systemic inflammation and T-cell dysfunctions were hallmarks of increased severity and further distinguished patients with similar acute respiratory severity by their distinct immune profiles, which correlated with differences in demographic and clinical complications. Notably, one critical subtype (SubF) was uniquely characterized by early excessive inflammation, insufficient anticoagulation, and fatty acid dysregulation, alongside higher incidences of hematologic, cardiac, and renal complications, and an elevated risk of long COVID. Among the severe subtypes, significant differences in viral clearance and early antiviral responses were observed, with one subtype (SubC) showing strong early T-cell cytotoxicity but a poor humoral response, slower viral clearance, and greater risks of chronic organ dysfunction and long COVID. These findings provide crucial insights into the complex and context-dependent nature of COVID-19 immune responses, highlighting the importance of personalized therapeutic strategies to improve both acute and long-term outcomes.

Infection-associated chronic conditions: Why Long Covid is our best chance to untangle Osler's web

The recognition of Long Covid has renewed efforts to understand other infection-associated chronic conditions (IACCs). Here, we describe how studies of Long Covid and other IACCs might inform one another. We argue for the importance of a coordinated research agenda addressing these debilitating illnesses.

Translating insights into therapies for Long Covid

Long Covid is defined by a wide range of symptoms that persist after the acute phase of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Commonly reported symptoms include fatigue, weakness, postexertional malaise, and cognitive dysfunction, with many other symptoms reported. Symptom range, duration, and severity are highly variable and partially overlap with symptoms of myalgic encephalomyelitis/chronic fatigue syndrome and other post-acute infectious syndromes, highlighting opportunities to define shared mechanisms of pathogenesis. Potential mechanisms of Long Covid are diverse, including persistence of viral reservoirs, dysregulated immune responses, direct viral damage of tissues targeted by SARS-CoV-2, inflammation driven by reactivation of latent viral infections, vascular endothelium activation or dysfunction, and subsequent thromboinflammation, autoimmunity, metabolic derangements, microglial activation, and microbiota dysbiosis. The heterogeneity of symptoms and baseline characteristics of people with Long Covid, as well as the varying states of immunity and therapies given at the time of acute infection, have made etiologies of Long Covid difficult to determine. Here, we examine progress on preclinical models for Long Covid and review progress being made in clinical trials, highlighting the need for large human studies and further development of models to better understand Long Covid. Such studies will inform clinical trials that will define treatments to benefit those living with this condition.

Mechanisms of long COVID and the path toward therapeutics

Long COVID, a type of post-acute sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (PASC) defined by medically unexplained symptoms following infection with SARS-CoV-2, is a newly recognized infection-associated chronic condition that causes disability in some people. Substantial progress has been made in defining its epidemiology, biology, and pathophysiology. However, there is no cure for the tens of millions of people believed to be experiencing long COVID, and industry engagement in developing therapeutics has been limited. Here, we review the current state of knowledge regarding the biology and pathophysiology of long COVID, focusing on how the proposed mechanisms explain the physiology of the syndrome and how they provide a rationale for the implementation of a broad experimental medicine and clinical trials agenda. Progress toward preventing and curing long COVID and other infection-associated chronic conditions will require deep and sustained investment by funders and industry.

SARS-CoV-2-specific CD8+ T cells from people with long COVID establish and maintain effector phenotype and key TCR signatures over 2 years

Long COVID occurs in a small but important minority of patients following COVID-19, reducing quality of life and contributing to healthcare burden. Although research into underlying mechanisms is evolving, immunity is understudied. SARS-CoV-2-specific T cell responses are of key importance for viral clearance and COVID-19 recovery. However, in long COVID, the establishment and persistence of SARS-CoV-2-specific T cells are far from clear, especially beyond 12 mo postinfection and postvaccination. We defined ex vivo antigen-specific B cell and T cell responses and their T cell receptors (TCR) repertoires across 2 y postinfection in people with long COVID. Using 13 SARS-CoV-2 peptide-HLA tetramers, spanning 11 HLA allotypes, as well as spike and nucleocapsid probes, we tracked SARS-CoV-2-specific CD8+ and CD4+ T cells and B-cells in individuals from their first SARS-CoV-2 infection through primary vaccination over 24 mo. The frequencies of ORF1a- and nucleocapsid-specific T cells and B cells remained stable over 24 mo. Spike-specific CD8+ and CD4+ T cells and B cells were boosted by SARS-CoV-2 vaccination, indicating immunization, in fully recovered and people with long COVID, altered the immunodominance hierarchy of SARS-CoV-2 T cell epitopes. Meanwhile, influenza-specific CD8+ T cells were stable across 24 mo, suggesting no bystander-activation. Compared to total T cell populations, SARS-CoV-2-specific T cells were enriched for central memory phenotype, although the proportion of central memory T cells decreased following acute illness. Importantly, TCR repertoire composition was maintained throughout long COVID, including postvaccination, to 2 y postinfection. Overall, we defined ex vivo SARS-CoV-2-specific B cells and T cells to understand primary and recall responses, providing key insights into antigen-specific responses in people with long COVID.

Post-acute sequelae of COVID infection and cerebral venous outflow disorders: Overlapping symptoms and mechanisms?

Neurological long Covid (NLC) is a major post-acute sequela of SARS-CoV-2 infection, affecting up to 10% of infected patients. The clinical presentation of patients with NLC is varied, but general NLC symptoms have been noted to closely mimic symptoms of cerebral venous outflow disorders (CVD). Here we review key literature and discuss evidence supporting this comparison. We also aimed to describe the similarity between CVD symptomatology and neuro-NLC symptoms from two perspectives: a Twitter-distributed survey for long covid sufferers to estimate nature and frequency of neurological symptoms, and through a small cohort of patients with long covid who underwent CVD work up per our standard workflow. Over 700 patients responded, and we argue that there is a close symptom overlap with those of CVD. CVD workup in a series of 6 patients with neurological long COVID symptoms showed jugular vein stenosis by CT venography and varying degrees of increased intracranial pressure. Finally, we discuss the potential pathogenic association between vascular inflammation, associated with COVID-19 infection, venous outflow congestion, and its potential involvement in NLC.

Antibody responses to common viruses according to COVID-19 severity and postacute sequelae of COVID-19

Limited research suggests that certain viruses reactivate in severe-acute-respiratory-syndrome-coronavirus 2 infection, contributing to the development of postacute sequelae of COVID-19 (PASC). We examined 1083 infected individuals from a population-based cohort, and assessed differences in plasma immunoglobulin (Ig)G and immunoglobulin A levels against Epstein-Barr virus (EBV), cytomegalovirus, varicella zoster virus (VZV), BK polyomavirus, KI polyomavirus, WU polyomavirus (WUPyV), respiratory syncytial virus, and Adv-36 according to the severity of previous COVID-19 and PASC history. Individuals who had experienced severe COVID-19 had higher antibody responses to latent viruses. Ever PASC, active persistent PASC, and PASC with neuropsychiatric symptoms were associated with higher immnoglobulin G to EBV early antigen-diffuse, VZV, and WUPyV even among individuals without previous severe COVID-19.

Postacute Sequelae of COVID (PASC or Long COVID): An Evidenced-Based Approach

While the acute manifestations of infectious diseases are well known, in some individuals, symptoms can either persist or appear after the acute period. Postviral fatigue syndromes are recognized with other viral infections and are described after coronavirus disease 2019 (COVID-19). We have a growing number of individuals with symptoms that persist for weeks, months, and years. Here, we share the evidence regarding the abnormalities associated with postacute sequelae of COVID-19 (PASC) and therapeutics. We describe physiological and biochemical abnormalities seen in individuals reporting PASC. We describe the several evidence-based interventions to offer patients. It is expected that this growing understanding of the mechanisms driving PASC and the benefits seen with certain therapeutics may not only lead to better outcomes for those with PASC but may also have the potential for understanding and treating other postinfectious sequelae.

Early biological markers of post-acute sequelae of SARS-CoV-2 infection

To understand the roles of acute-phase viral dynamics and host immune responses in post-acute sequelae of SARS-CoV-2 infection (PASC), we enrolled 136 participants within 5 days of their first positive SARS-CoV-2 real-time PCR test. Participants self-collected up to 21 nasal specimens within the first 28 days post-symptom onset; interviewer-administered questionnaires and blood samples were collected at enrollment, days 9, 14, 21, 28, and month 4 and 8 post-symptom onset. Defining PASC as the presence of any COVID-associated symptom at their 4-month visit, we compared viral markers (quantity and duration of nasal viral RNA load, infectious viral load, and plasma N-antigen level) and host immune markers (IL-6, IL-10, TNF-α, IFN-α, IFN-γ, MCP, IP-10, and Spike IgG) over the acute period. Compared to those who fully recovered, those reporting PASC demonstrated significantly higher maximum levels of SARS-CoV-2 RNA and N-antigen, burden of RNA and infectious viral shedding, and lower Spike-specific IgG levels within 9 days post-illness onset. No significant differences were identified among a panel of host immune markers. Our results suggest early viral dynamics and the associated host immune responses play a role in the pathogenesis of PASC, highlighting the importance of understanding early biological markers in the natural history of PASC.

Uncovering the Contrasts and Connections in PASC: Viral Load and Cytokine Signatures in Acute COVID-19 versus Post-Acute Sequelae of SARS-CoV-2 (PASC)

The recent global COVID-19 pandemic has had a profound and enduring impact, resulting in substantial loss of life. The scientific community has responded unprecedentedly by investigating various aspects of the crisis, particularly focusing on the acute phase of COVID-19. The roles of the viral load, cytokines, and chemokines during the acute phase and in the context of patients who experienced enduring symptoms upon infection, so called Post-Acute Sequelae of COVID-19 or PASC, have been studied extensively. Here, in this review, we offer a virologist's perspective on PASC, highlighting the dynamics of SARS-CoV-2 viral loads, cytokines, and chemokines in different organs of patients across the full clinical spectrum of acute-phase disease. We underline that the probability of severe or critical disease progression correlates with increased viral load levels detected in the upper respiratory tract (URT), lower respiratory tract (LRT), and plasma. Acute-phase viremia is a clear, although not unambiguous, predictor of PASC development. Moreover, both the quantity and diversity of functions of cytokines and chemokines increase with acute-phase disease severity. Specific cytokines remain or become elevated in the PASC phase, although the driving factor of ongoing inflammation found in patients with PASC remains to be investigated. The key findings highlighted in this review contribute to a further understanding of PASC and their differences and overlap with acute disease.

Impact of Post-Acute Sequelae of COVID-19 on Lives of Patients Post-Intensive Care Unit Discharge: A Cross-Sectional Study

OBJECTIVES

Post-acute sequelae of SARS-CoV-2 (PASC) are known for their prolonged and persistent effects on patients. This study aimed to investigate the impact of the PASC on the quality of life (QOL) of patients, their levels of activity participation, and satisfaction with these levels, in addition to exploring whether the duration of post-intensive care unit (ICU) discharge is associated with the effects of PASC.

SUBJECT AND METHODS

This cross-sectional study included 134 patients with COVID-19 discharged from an ICU in Kuwait. Data were collected using two validated questionnaires: the World Health Organization Quality of Life-Brief (WHOQOL-BREF) and Satisfaction with Daily Occupations. Additionally, demographic information was collected, and 11 categories of related symptoms were investigated.

RESULTS

Most patients reported health issues post-ICU discharge. Furthermore, most PASC-related symptoms decreased over time, whereas a few increased. Notably, we observed a negative association between post-discharge duration and overall improvement in level of participation in activities of daily living. However, patients discharged from the ICU for more than 6 months demonstrated higher satisfaction with functional performance and improved QOL. Additionally, patients who received rehabilitation, and were vaccinated were less likely to have poor QOL. No significant sex differences were observed in the WHOQOL-BREF score.

CONCLUSION

PASC adversely affected the daily functioning of patients, especially in leisure, social, and religious aspects. However, these effects lessened over time, with corresponding improvement in QOL. Additionally, patient satisfaction with functional performance increased over time. These findings shed light on the rehabilitation needs of patients with COVID-19.

A systematic review and meta-analysis, investigating dose and time of fluvoxamine treatment efficacy for COVID-19 clinical deterioration, death, and Long-COVID complications

There have been 774,075,242 cases of COVID-19 and 7,012,986 deaths worldwide as of January 2024. In the early stages of the pandemic, there was an urgent need to reduce the severity of the disease and prevent the need for hospitalization to avoid stress on healthcare systems worldwide. The repurposing of drugs to prevent clinical deterioration of COVID-19 patients was trialed in many studies using many different drugs. Fluvoxamine (an SSRI and sigma-1 receptor agonist) was initially identified to potentially provide beneficial effects in COVID-19-infected patients, preventing clinical deterioration and the need for hospitalization. Fourteen clinical studies have been carried out to date, with seven of those being randomized placebo-controlled studies. This systematic review and meta-analysis covers the literature from the outbreak of SARS-CoV-2 in late 2019 until January 2024. Search terms related to fluvoxamine, such as its trade names and chemical names, along with words related to COVID-19, such as SARS-CoV-2 and coronavirus, were used in literature databases including PubMed, Google Scholar, Scopus, and the ClinicalTrials.gov database from NIH, to identify the trials used in the subsequent analysis. Clinical deterioration and death data were extracted from these studies where available and used in the meta-analysis. A total of 7153 patients were studied across 14 studies (both open-label and double-blind placebo-controlled). 681 out of 3553 (19.17%) in the standard care group and 255 out of 3600 (7.08%) in the fluvoxamine-treated group experienced clinical deterioration. The estimated average log odds ratio was 1.087 (95% CI 0.200 to 1.973), which differed significantly from zero (z = 2.402, p = 0.016). The seven placebo-controlled studies resulted in a log odds ratio of 0.359 (95% CI 0.1111 to 0.5294), which differed significantly from zero (z = 3.103, p = 0.002). The results of this study identified fluvoxamine as effective in preventing clinical deterioration, and subgrouping analysis suggests that earlier treatment with a dose of 200 mg or above provides the best outcomes. We hope the outcomes of this study can help design future studies into respiratory viral infections and potentially improve clinical outcomes.

The Potential Role of Viral Persistence in the Post-Acute Sequelae of SARS-CoV-2 Infection (PASC)

The infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is associated not only with the development of acute disease but also with long-term symptoms or post-acute sequelae of SARS-CoV-2 (PASC). Multiple lines of evidence support that some viral antigens and RNA can persist for up to 15 months in multiple organs in the body, often after apparent clearance from the upper respiratory system, possibly leading to the persistence of symptoms. Activation of the immune system to viral antigens is observed for a prolonged time, providing indirect evidence of the persistence of viral elements after acute infection. In the gastrointestinal tract, the persistence of some antigens could stimulate the immune system, shaping the local microbiota with potential systemic effects. All of these interactions need to be investigated, taking into account predisposing factors, multiplicity of pathogenic mechanisms, and stratifying populations of vulnerable individuals, particularly women, children, and immunocompromised individuals, where SARS-CoV-2 may present additional challenges.

Yin and yang of interferons: lessons from the coronavirus disease 2019 (COVID-19) pandemic

The host immune response against severe acute respiratory syndrome coronavirus 2 includes the induction of a group of natural antiviral cytokines called interferons (IFNs). Although originally recognized for their ability to potently counteract infections, the mechanistic functions of IFNs in patients with varying severities of coronavirus disease 2019 (COVID-19) have highlighted a more complex scenario. Cellular and molecular analyses have revealed that timing, location, and subtypes of IFNs produced during severe acute respiratory syndrome coronavirus 2 infection play a major role in determining disease progression and severity. In this review, we summarize what the COVID-19 pandemic has taught us about the protective and detrimental roles of IFNs during the inflammatory response elicited against a new respiratory virus across different ages and its longitudinal consequences in driving the development of long COVID-19.

Bibliometric analysis and key messages of integrating Chinese and Western Medicine for COVID-19

Background

The coronavirus disease 2019 (COVID-19) has been a global pandemic since it broke out, and integrated Chinese and Western medicine (ICWM) has played an important role in the prevention and treatment of COVID-19. We aimed to analyze the published literature on ICWM for COVID-19 at home and abroad, and compare their differences on hotspots and research fronts.

Methods

Publications before Oct 31, 2022 were retrieved from the Web of Science core database (WOS), PubMed, China National Knowledge Infrastructure database (CNKI), Wanfang Data Knowledge Service Platform (Wanfang), China Science and Technology Journal Database (VIP), China Biology Medicine disc (CBM), CiteSpace and VOSviewer to summarize the basic characteristics of publications, countries, institutions, keywords, and citations.

Results

We included 580 English papers and 1727 Chinese papers in this study. The development trends in China and other countries are relatively asynchronous and show a smooth growth trend for the future. The most productive countries were China, India, and the United States, while the most productive domestic research institution was the Beijing University of Chinese Medicine. The clustering analysis of high-frequency keywords showed that Chinese literature focused on clinical studies of ICWM for COVID-19, such as retrospective studies, clinical features, and traditional Chinese medicine syndrome analysis, while English literature focused on therapeutic mechanism studies and evidence-based medicine studies, such as systematic reviews and meta-analysis, and both of them paid attention to network pharmacological research and Qingfei Paidu Decoction. Sorting out the top 10 highly cited articles, Huang CL's article published in Lancet in 2020 was regarded as a cornerstone in the field.

Conclusion

The treatment of COVID-19 by ICWM has become a worldwide research hotspot. Although there are differences in the specific contents among countries, the development trend of research types to the mechanism of action, and the development trend of research contents to the recovery period treatment and the prevention of COVID-19 by ICWM are consistent.