Pediatric COVID-19: Immunopathogenesis, Transmission and Prevention

Altered brain glucose metabolism in COVID-19 disease: an activation likelihood estimation meta-analysis of PET studies

COVID-19 disease, caused by the SARS-CoV-2 virus, has significantly altered modern society and lifestyles. We investigated its impact on brain glucose metabolism by meta-analyzing existing studies that utilized 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) scans of the brain. We conducted a systematic search of MEDLINE and EMBASE databases from inception to August 2024 for English-language publications using the keywords "positron emission tomography", and "COVID-19". We included original research articles that reported changes in brain glucose metabolism following COVID-19 disease. ALE values from these studies were aggregated and tested against a null hypothesis that anticipated a random distribution of ALE values, which proved to be significantly higher than chance. We identified nine papers that met our inclusion criteria. Significant increases in brain glucose metabolism were noted in the left anterior cingulate gyrus, right thalamus, and brainstem. In children with COVID-19 disease, decreased glucose metabolism was observed in the right and left cerebellum, left amygdala/hippocampus, left anterior cingulate gyrus, and right amygdala. In adults with COVID-19 disease, decreased metabolism was seen in the right temporal lobe, brainstem (acute phase), left occipital lobe, left and right temporal lobe (chronic phase). In conclusion, COVID-19 disease impacts brain glucose metabolism, typically manifesting as areas of decreased metabolism in 18F-FDG PET scans, though increases are also observed. These changes in metabolism vary with the patient's age and the time elapsed between the diagnosis of COVID-19 disease and the PET scan.

COVID-19 vaccination in children: a public health priority

OBJECTIVE

Covid-19 had a direct impact on children's health. The aim of this review was to analyze epidemiological and clinical data, the consequences of the pandemic, and vaccination aspects in this group.

SOURCES OF DATA

The searches were carried out from January 2020 to November 2022, in the MEDLINE databases (PubMed) and publications of the Brazilian Ministry of Health and the Brazilian Society of Pediatrics.

SUMMARY OF FINDINGS

Covid-19 has a mild presentation in most children; however, the infection can progress to the severe form and, in some cases, to MIS-C. The prevalence of the so-called long Covid in children was 25.24%. Moreover, several indirect impacts occurred on the health of children and adolescents. Vaccination played a crucial role in enabling the reduction of severe disease and mortality rates. Children and adolescents, as a special population, were excluded from the initial clinical trials and, therefore, vaccination was introduced later in this group. Despite its importance, there have been difficulties in the efficient implementation of vaccination in the pediatric population. The CoronaVac vaccines are authorized in Brazil for children over three years of age and the pediatric presentations of the Pfizer vaccine have shown significant effectiveness and safety.

CONCLUSIONS

Covid-19 in the pediatric age group was responsible for the illness and deaths of a significant number of children. For successful immunization, major barriers have to be overcome. Real-world data on the safety and efficacy of several pediatric vaccines is emphasized, and the authors need a uniform message about the importance of immunization for all children.

Association of cellular immunity with severity of COVID-19 from the perspective of antigen-specific memory T cell responses and cross-reactivity

Coronaviruses regularly cause outbreaks of zoonotic diseases characterized by severe pneumonia. The new coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused the global pandemic disease COVID-19 that began at the end of 2019 and spread rapidly owing to its infectious nature and rapidly progressing pneumonia. Although the infectivity of SARS-CoV-2 is high, indicated by the worldwide spread of the disease in a very short period, many individuals displayed only subclinical infection, and some of them transmitted the disease to individuals who then developed a severe symptomatic infection. Furthermore, there are differences in the severity of infection across countries, which can be attributed to factors such as the emergence of viral mutations in a short period of time as well as to the immune responses to viral factors. Anti-viral immunity generally consists of neutralizing antibodies that block viral infection and cytotoxic CD8+ T cells that eliminate the virus-infected cells. There is compelling evidence for the role of neutralizing antibodies in protective immunity in SARS-CoV-2 infection. However, the role of CD4+ and CD8+ T cells after the viral entry is complex and warrants a comprehensive discussion. Here, we discuss the protection afforded by cellular immunity against initial infection and development of severe disease. The initial failure of cellular immunity to control the infection worsens the clinical outcomes and functional profiles that inflict tissue damage without effectively eliminating viral reservoirs, while robust T cell responses are associated with mild outcomes. We also discuss persistent long-lasting memory T cell-mediated protection after infection or vaccination, which is rather complicated as it may involve SARS-CoV-2-specific cytotoxic T lymphocytes or cross-reactivity with previously infected seasonal coronaviruses, which are largely related to HLA genotypes. In addition, cross-reactivity with mutant strains is also discussed. Lastly, we discuss appropriate measures to be taken against the disease for immunocompromised patients. In conclusion, we provide evidence and discuss the causal relationship between natural infection- or vaccine-mediated memory T cell immunity and severity of COVID-19. This review is expected to provide a basis to develop strategies for the next generation of T cell-focused vaccines and aid in ending the current pandemic.

Younger Children Develop Higher Effector Antibody Responses to SARS-CoV-2 Infection

Background

The basis of the less severe clinical presentation of coronavirus disease 2019 (COVID-19) in children as compared with adults remains incompletely understood. Studies have suggested that a more potent boosting of immunity to endemic common cold coronaviruses (HCoVs) may protect children.

Methods

To test this hypothesis, we conducted a detailed analysis of antibodies induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children aged 2 months to 14 years.

Results

Younger children had higher titers of antibodies to SARS-CoV-2 receptor binding domain (RBD), S1 but not S2 domain, and total spike (S) protein, higher avidity RBD immunoglobulin G, and higher titers of neutralizing and complement-activating antibodies as compared with older children. In contrast, older children had higher titers of antibodies to HCoVs, which correlated with antibodies to the SARS-CoV-2 S2 domain but not with neutralizing or complement-activating antibodies.

Conclusions

These results reveal a unique capacity of young children to develop effector antibody responses to SARS-CoV-2 infection independently of their immunity to HCoVs.

Routine SARS-CoV-2 vaccination for all children

The SARS-CoV-2 pandemic has resulted in unprecedented health and economic losses. Children generally present with less severe disease from this virus compared with adults, yet neonates and children with COVID-19 can require hospitalization, and older children can develop severe complications, such as the multisystem inflammatory syndrome, resulting in >1500 deaths in children from COVID-19 since the onset of the pandemic. The introduction of effective SARS-CoV-2 vaccines in school-age children and adult populations combined with the emergence of new, more highly transmissible SARS-CoV-2 variants has resulted in a proportional increase of infections in young children. Here, we discuss (1) the current knowledge on pediatric SARS-CoV-2 infection and pathogenesis in comparison with adults, (2) the data on vaccine immunogenicity and efficacy in children, and (3) the benefits of early life SARS-CoV-2 vaccination.

Cellular immunity in patients with COVID-19: molecular biology, pathophysiology, and clinical implications

The COVID-19 pandemic is caused by the SARS-CoV-2 coronavirus. From the viewpoint of factors critical to contain the virus, the neutralizing antibodies to SARS-CoV-2 garner most of the attention, however, it is essential to acknowledge that it is the level of the virus-specific T cell and B cell response that forms a basis for an effective neutralizing antibody response. T cell responses develop early and correlate with the protection, but they are relatively attenuated in the severe disease, in part due to lymphopenia. Understanding the role of different T cell subpopulations in the protection or the COVID-19 pathogenesis is critical to the prevention and treatment. The expression profile of different T cell subpopulations varies with the COVID-19 severity and is associated with the degree of T cell responses and the disease outcome. The structural changes in the genome, transcriptome, and proteome of SARS-CoV-2 promote the emergence of new variants of the virus and can reduce its interaction with antibodies and result in avoiding the neutralization. There is a strong correlation between the number of virus-specific CD4 T cells and neutralizing IgG antibody titers against SARS-CoV-2. During the primary viral infection, there is a wide variation in the cellular and humoral immune responses, patients with severe and prolonged symptoms showing highly imbalanced cellular and humoral immune responses. This review focuses on the generation and clinical significance of cellular immunity in the protection against severe acute infection and reinfection, as well as the potential involvement of seasonal coronavirus-specific cross-reactive T cells in response to SARS-CoV-2.

COVID-19 in children: epidemic issues and candidate vaccines

ABSTRACT

A large-scale vaccination of coronavirus disease-19 (COVID-19) in adults has been conducted for nearly a year, and there is a growing recognition that immunization for children is also essential. It has been months since emergency use of pediatric COVID-19 vaccine was approved, we reviewed the prevalence and transmission of COVID-19 in children. The prevalence of COVID-19 in children is reduced due to vaccination even in a Delta prevalent period, so an increase in the vaccination rate is needed in children. Although the precise role of children in the transmission requires more research to uncover, they likely played a significant role, according to the available literature. We also described four candidate COVID-19 vaccines for children on their safety and immunogenicity and the impact of severe acute respiratory syndrome coronavirus 2 variants on childhood vaccination. Safety issues on pediatric vaccines post-approval, like adverse events following immunization and adverse events of special interest require studies on long-term and effective regulatory mechanisms.

Safety, Immunogenicity, and Efficacy of COVID-19 Vaccines in Adolescents, Children, and Infants: A Systematic Review and Meta-Analysis

Background

As the epidemic progresses, universal vaccination against COVID-19 has been the trend, but there are still some doubts about the efficacy and safety of COVID-19 vaccines in adolescents, children, and even infants.

Purpose

To evaluate the safety, immunogenicity, and efficacy of COVID-19 vaccines in the population aged 0–17 years.

Method

A comprehensive search for relevant randomized controlled trials (RCTs) was conducted in PubMed, Embase, and the Cochrane Library from inception to November 9, 2021. All data were pooled by RevMan 5.3 statistical software, with risk ratio (RR) and its 95% confidence interval as the effect measure. This study protocol was registered on PROSPERO (CRD42021290205).

Results

There was a total of six randomized controlled trials included in this systematic review and meta-analysis, enrolling participants in the age range of 3–17 years, and containing three types of COVID-19 vaccines. Compared with mRNA vaccines and adenovirus vector vaccines, inactivated vaccines have a more satisfactory safety profile, both after initial (RR 1.40, 95% CI 1.04–1.90, P = 0.03) and booster (RR 1.84, 95% CI 1.20–2.81, P = 0.005) vaccination. The risk of adverse reactions was significantly increased after the first and second doses, but there was no significant difference between the first two doses (RR 1.00, 95%CI 0.99–1.02, P = 0.60). Nevertheless, the two-dose regimen is obviously superior to the single-dose schedule for immunogenicity and efficacy. After booster vaccination, both neutralizing antibodies (RR 144.80, 95%CI 44.97–466.24, P < 0.00001) and RBD-binding antibodies (RR 101.50, 95%CI 6.44–1,600.76, P = 0.001) reach optimal levels, but the cellular immune response seemed not to be further enhanced. In addition, compared with younger children, older children and adolescents were at significantly increased risk of adverse reactions after vaccination, with either mRNA or inactivated vaccines, accompanied by a stronger immune response.

Conclusion

The available evidence suggests that the safety, immunogenicity and efficacy of COVID-19 vaccines are acceptable in people aged 3–17 years. However, there is an urgent need for additional multicenter, large-sample studies, especially in younger children under 3 years of age and even in infants, with long-term follow-up data.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021290205, identifier: CRD42021290205.

Adolescent COVID-19 Vaccine Decision-Making among Parents in Southern California

Adolescent COVID-19 vaccination has stalled at 53% in the United States. Vaccinating adolescents remains critical to preventing the continued transmission of COVID-19, the emergence of variants, and rare but serious disease in children, and it is the best preventive measure available to return to in-person schooling. We investigated parent–adolescent COVID-19 vaccine decision-making. Between 24 February and 15 March 2021, we conducted surveys and 12 focus groups with 46 parent–adolescent dyads in Southern California. Parents and adolescents completed a survey prior to participation in a focus group discussion, which focused on exploring COVID-19 vaccine acceptance or uncertainty and was guided by the 5C vaccine hesitancy model. Parents uncertain about vaccinating adolescents expressed low vaccine confidence and high COVID-19 disease risk complacency. Parents who accepted COVID-19 vaccination for adolescents expressed high confidence in health authority vaccine recommendations, high perceived COVID-19 risk, and collective responsibility to vaccinate children. Additionally, unique pandemic-related factors of vaccine acceptance included vaccinating for emotional health, resuming social activities, and vaccine mandates. Among parents, 46% were willing to vaccinate their adolescent, 11% were not, and 43% were unsure. Among adolescents, 63% were willing to vaccinate. Despite vaccine availability, 47% of adolescents remain unvaccinated against COVID-19. Factors associated with vaccine uncertainty and acceptability inform health care practitioner, school, community, and public health messaging to reach parents and adolescents.

Pediatric Functional Abdominal Pain Disorders following COVID-19

BACKGROUND

Functional abdominal pain disorders (FAPD) are a group of functional gastrointestinal disorders with multifactorial etiology and are subclassified using Rome IV criteria into a series of clinically distinct entities represented by irritable bowel syndrome, functional dyspepsia, abdominal migraine and functional abdominal pain that is not otherwise specified. Digestive functional disorders associated with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) may be mediated by the involvement of complex pathogenic mechanisms, which have been under investigation in children since the beginning of the coronavirus disease pandemic (COVID-19).

METHODS

In this retrospective, observational descriptive and analytical study, we investigated the presence of chronical functional abdominal pain in preschool children (4-6 years old) from the south-west of Romania in the pre-pandemic (18 cases) and COVID-19 pandemic period (34 cases), as well as the association with the COVID-19 positive and COVID-19 negative statuses, gender, environment origin, and viral infection-associated symptoms. Age-specific Rome IV criteria were used to diagnose functional abdominal pain. We performed an integrated statistical analysis of the results utilizing an electronic database in which we compared the data in order to assess the impact of COVID-19 on the clinical-epidemiological parameters analyzed.

RESULTS

In the pre-pandemic group, irritable bowel syndrome predominated (77.8%), followed by functional dyspepsia (22.2%), the other types of functional abdominal pain being absent, while for the pandemic group, irritable bowel syndrome was the most common (79.4%), followed by abdominal migraine (11.8%), abdominal dyspepsia (5.9%) and functional abdominal pain not otherwise specified (2.9%). We found a female/male ratio difference of 0.84 and an urban/rural ratio of 1.83 in favor of the pandemic group. These discrepancies were mainly caused by the differences between the COVID-19 positive and negative pandemic groups, where we observed statistical association of the positive pandemic group with IBS and urban environment, and a tendency of FAPDs diagnostic mainly with males. The predominant symptoms associated with COVID-19 positive cases were digestive (60.9%) or respiratory (39.1%).

CONCLUSIONS

Our study demonstrates viral-mediated sensitivity of the gastrointestinal tract in preschool children, considering different clinical-epidemiological profiles related to the prevalence of FAPD and according to gender and environment origin, while the contribution of the pandemic context remains to be demonstrated in larger studies.

Intestinal microbiota composition of children with infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and multisystem inflammatory syndrome (MIS-C)

Microbiota composition may play a role in the development, prognosis, or post-infection of COVID-19. There are studies evaluating the microbiota composition at the time of diagnosis and during the course of COVID-19, especially in adults, while studies in children are limited and no study available in children with multisystem inflammatory syndrome in children (MIS-C). This study was planned to compare intestinal microbiota composition in children diagnosed with MIS-C and acute COVID-19 infection with healthy children. In this prospective multicenter study, 25 children diagnosed with MIS-C, 20 with COVID-19 infection, and 19 healthy children were included. Intestinal microbiota composition was evaluated by 16 s rRNA gene sequencing. We observed changes of diversity, richness, and composition of intestinal microbiota in MIS-C cases compared to COVID-19 cases and in the healthy controls. The Shannon index was higher in the MIS-C group than the healthy controls (p < 0.01). At phylum level, in the MIS-C group, a significantly higher relative abundance of Bacteroidetes and lower abundance of Firmicutes was found compared to the control group. Intestinal microbiota composition changed in MIS-C cases compared to COVID-19 and healthy controls, and Faecalibacterium prausnitzii decreased; Bacteroides uniformis, Bacteroides plebeius, Clostridium ramosum, Eubacterium dolichum, Eggerthella lenta, Bacillus thermoamylovorans, Prevotella tannerae, and Bacteroides coprophilus were dominant in children with MIS-C. At species level, we observed decreased Faecalibacterium prausnitzii, and increased Eubacterium dolichum, Eggerthella lenta, and Bacillus thermoamylovorans in children with MIS-C and increased Bifidobacterium adolescentis and Dorea formicigenerasus in the COVID-19 group. Our study is the first to evaluate the microbiota composition in MIS-C cases. There is a substantial change in the composition of the gut microbiota: (1) reduction of F. prausnitzii in children with MIS-C and COVID-19; (2) an increase of Eggerthella lenta which is related with autoimmunity; and (3) the predominance of E. dolichum is associated with metabolic dysfunctions and obesity in children with MIS-C.

CONCLUSIONS

 Alterations of the intestinal microbiota might be part of pathogenesis of predisposing factor for MIS-C. It would be beneficial to conduct more extensive studies on the cause-effect relationship of these changes in microbiota composition and their effects on long-term prognosis.

WHAT IS KNOWN

• Microbiota composition may play a role in the development, prognosis, or post-infection of COVID-19.  • However, the number of studies on children is limited, and no study on multisystem inflammatory syndrome in children is currently available (MIS-C).

WHAT IS NEW

• In individuals with MIS-C, the composition of the gut microbiota changed dramatically. • Decreased Faecalibacterium prausnitzii have been observed, increased Eggerthella lenta, which was previously linked to autoimmunity, and predominance of Eubacterium dolichum which was linked to metabolic dysfunction and obesity.

Antioxidant status in children and adolescents with COVID-19

Background. The COVID-19 pandemic has raised the importance of this problem to the first stage and has affected healthcare system around the world. Despite the more favorable COVID-19 course, the child population should be at focus of special attention, due to the active participation in its distribution. The course of COVID-19 includes a cascade of pathological processes accompanied by the generation of reactive oxygen species, which can have extremely negative consequences for the developing organism. The research of these processes in children is vital and will improve the effectiveness of preventive and therapeutic measures. The aim: to analyze changes in enzymatic and non-enzymatic links in the antioxidant defense in children and adolescents with diagnosed COVID-19 infection.Materials and methods. 17 children and adolescents (average age – 12.35 ± 4.01 years) were examined, including 8 boys (47 %) and 9 girls (53 %) with COVID-19 infection. The control group of children and adolescents (practically healthy) according to the «copy-pair» principle was selected. We used spectrophotometric methods.Results. In the group of children and adolescents with diagnosed COVID-19 infection, there were lower levels of total antioxidant activity (p < 0.0001), superoxide dismutase activity (p < 0.0001), content of reduced glutathione (p = 0.048) and retinol (p = 0.015), increase in glutathione reductase activity (p = 0.015) relative to the control.Conclusion. The obtained data indicate the insufficiency of antioxidant system components number in children and adolescents with diagnosed COVID-19 infection and indicate the advisability of antioxidant therapy using to stabilize these indicators.

Elucidating T Cell and B Cell Responses to SARS-CoV-2 in Humans: Gaining Insights into Protective Immunity and Immunopathology

The SARS-CoV-2 pandemic is an unprecedented epochal event on at least two fronts. Firstly, in terms of the rapid spread and the magnitude of the outbreak, and secondly, on account of the equally swift response of the scientific community that has galvanized itself into action and has successfully developed, tested and deployed highly effective and novel vaccines in record time to combat the virus. The sophistication and diversification of the scientific toolbox we now have at our disposal has enabled us to interrogate both the breadth and the depth of the immune response to a degree that is unparalleled in recent memory. In terms of our understanding of what is critical to contain the virus and mitigate the effects the pandemic, neutralizing antibodies to SARS-CoV-2 garner most of the attention, however, it is essential to recognize that it is the quality and the fitness of the virus-specific T cell and B cell response that lays the foundation and the backdrop for an effective neutralizing antibody response. In this report, we will review some of the key findings that have helped define and delineate some of the essential attributes of T and B cell responses in the setting of SARS-CoV-2 infection.

Natural Bioactive Molecules: An Alternative Approach to the Treatment and Control of COVID-19

Several coronaviruses (CoVs) have been associated with serious health hazards in recent decades, resulting in the deaths of thousands around the globe. The recent coronavirus pandemic has emphasized the importance of discovering novel and effective antiviral medicines as quickly as possible to prevent more loss of human lives. Positive-sense RNA viruses with group spikes protruding from their surfaces and an abnormally large RNA genome enclose CoVs. CoVs have already been related to a range of respiratory infectious diseases possibly fatal to humans, such as MERS, SARS, and the current COVID-19 outbreak. As a result, effective prevention, treatment, and medications against human coronavirus (HCoV) is urgently needed. In recent years, many natural substances have been discovered with a variety of biological significance, including antiviral properties. Throughout this work, we reviewed a wide range of natural substances that interrupt the life cycles for MERS and SARS, as well as their potential application in the treatment of COVID-19.

Special Issue "Immune Ontogeny and Vaccination in Early Life: How the Non-Human Primate Model Can Help Expand the Current Knowledge in Pediatric Immunology and Infectious Diseases Research"

The development of the immune system requires a number of changes that occur during the first months of life [...].