Early immune responses and prognostic factors in children with COVID-19: a single-center retrospective analysis

Immunophenotype of lymphocytes and real-world outcome of COVID-19 infection in children with hematology and oncology

BACKGROUND

Patients with immunocompromise were suspected to encounter a high risk for severe coronavirus disease 2019 (COVID-19) infection on early period; however, data is lacking nowadays and immune response remain unclear.

METHODS

In this retrospective study, internet questionnaire survey and medical records were acquired in pediatric hematology oncology patients. Clinical severity, immunological characteristics, and outcomes were analyzed from December 1, 2022 to January 31, 2023 at the 3rd year of pandemic in China.

RESULTS

A total of 306 patients were included, with 21 patients (6.9%) asymptomatic, 262 (85.6%) mild severity, 17 (5.6%) moderate severity, 5 (1.6%) severe severity, and 1 (0.3%) critical severity. Seventy-eight (25.5%) patients were on intensive chemotherapy, and 32.0% children were on maintenance chemotherapy. Delays in cancer therapy occurred in 86.7% patients. Univariable analysis revealed active chemotherapy (P < 0.0001), long duration of symptom (P < 0.0001), low lymphocytes count (P = 0.095), low CD3 + and CD8 + T cell count (P = 0.013, P = 0.022), high percentage of CD4 + TCM (P = 0.016), and low percentage of transitional B cells (P = 0.045) were high risk factors for severe COVID-19 infection. Cox regression model showed that the absolute lymphocytes count (P = 0.027) and long duration of symptom (P = 0.002) were the independent factors for severity. Patients with CD8 + dominant and B cell depletion subtype wasn't related with severity, but had higher percentage of CD8 + effector memory T cells (TEM) and terminally differentiated effector memory T cells (TEMRA) (P < 0.001, P < 0.001), and a longer COVID-19 duration (P = 0.045).

CONCLUSION

The severity was relatively mild in children with immunodeficiencies in the third year of COVID-19 pandemic. Low lymphocyte count and long duration of symptom were the independent risk factors with COVID-19 severity. Delays in cancer care remain a major concern and the long outcome is pending.

Risk Factors for Pediatric Critical COVID-19: A Systematic Review and Meta-Analysis

Background

Risk stratification is a cornerstone of the Pediatric Infectious Diseases Society COVID-19 treatment guidance. This systematic review and meta-analysis aimed to define the clinical characteristics and comorbidities associated with critical COVID-19 in children and adolescents.

Methods

Two independent reviewers screened the literature (Medline and EMBASE) for studies published through August 2023 that reported outcome data on patients aged ≤21 years with COVID-19. Critical disease was defined as an invasive mechanical ventilation requirement, intensive care unit admission, or death. Random effects models were used to estimate pooled odds ratios (OR) with 95% confidence intervals (CI), and heterogeneity was explored through subgroup analyses.

Results

Among 10,178 articles, 136 studies met the inclusion criteria for review. Data from 70 studies, which collectively examined 172,165 children and adolescents with COVID-19, were pooled for meta-analysis. In previously healthy children, the absolute risk of critical disease from COVID-19 was 4% (95% CI, 1%-10%). Compared with no comorbidities, the pooled OR for critical disease was 3.95 (95% CI, 2.78-5.63) for presence of one comorbidity and 9.51 (95% CI, 5.62-16.06) for ≥2 comorbidities. Key risk factors included cardiovascular and neurological disorders, chronic pulmonary conditions (excluding asthma), diabetes, obesity, and immunocompromise, all with statistically significant ORs >2.00.

Conclusions

While the absolute risk for critical COVID-19 in children and adolescents without underlying health conditions is relatively low, the presence of one or more comorbidities was associated with markedly increased risk. These findings support the importance of risk stratification in tailoring pediatric COVID-19 management.

Acute necrotizing encephalopathy in children with COVID-19: a retrospective study of 12 cases

Background

Acute necrotizing encephalopathy (ANE) is a devastating neurologic condition that can arise following a variety of systemic infections, including influenza and SARS-Cov-2. The clinical features of COVID-19-associated ANE in pediatric patients based on multi-case data have not yet been described and remain obscure. We reviewed 12 pediatric patients to better describe the clinical features of ANE with COVID-19.

Methods

We retrospectively collected and summarized the clinical features of ANE in children with COVID-19. Clinical data were collected from 12 children, including their general status, clinical symptoms, laboratory tests, and neuroimaging features.

Results

Among the subjects, 10 were over 5 years old and they accounted for 83.33%. A large percentage of those affected (66.67%) were females. The major manifestations included fever (100%), impaired consciousness (100%), and convulsions (75%). We determined that increased interleukin (IL)-6 and IL-10, and tumor necrosis factor-α and interferon gamma were not predictive of severe ANE and mortality in children with COVID-19 in this study. All children presented with abnormal neuroimaging with multiple and symmetrically distributed lesions, involving the thalamus, basal ganglia, cerebellum, and brain hemispheres. Eight of the 12 children died, resulting in a mortality rate of 66.67%, and 75% of these children were females. Importantly, we found the timely administration of mannitol after an acute onset of convulsions or disturbance of consciousness may be decreased the high mortality induced by ANE children with COVID-19.

Conclusion

COVID-19 associated with ANE in children is characterized by sudden symptom onset, rapid disease progression, and high mortality.

T Lymphocyte Subset Counts and Interferon-Gamma Production in Adults and Children with COVID-19: A Narrative Review

Adults and children exhibit a broad range of clinical outcomes from SARS-CoV-2 infection, with minimal to mild symptoms, especially in the pediatric age. However, some children present with a severe hyperinflammatory post-infectious complication named multisystem inflammatory syndrome in children (MIS-C), mainly affecting previously healthy subjects. Understanding these differences is still an ongoing challenge, that can lead to new therapeutic strategies and avoid unfavorable outcomes. In this review, we discuss the different roles of T lymphocyte subsets and interferon-γ (IFN-γ) in the immune responses of adults and children. Lymphopenia can influence these responses and represent a good predictor for the outcome, as reported by most authors. The increased IFN-γ response exhibited by children could be the starting point for the activation of a broad response that leads to MIS-C, with a significantly higher risk than in adults, although a single IFN signature has not been identified. Multicenter studies with large cohorts in both age groups are still needed to study SARS-CoV-2 pathogenesis with new tools and to understand how is possible to better modulate immune responses.

The Role of Immunity in the Pathogenesis of SARS-CoV-2 Infection and in the Protection Generated by COVID-19 Vaccines in Different Age Groups

This study aims to review the available data regarding the central role of immunity in combating SARS-CoV-2 infection and in the generation of protection by vaccination against COVID-19 in different age groups. Physiologically, the immune response and the components involved in it are variable, both functionally and quantitatively, in neonates, infants, children, adolescents, and adults. These immunological differences are mirrored during COVID-19 infection and in the post-vaccination period. The outcome of SARS-CoV-2 infection is greatly dependent on the reaction orchestrated by the immune system. This is clearly obvious in relation to the clinical status of COVID-19 infection, which can be symptomless, mild, moderate, or severe. Even the complications of the disease show a proportional pattern in relation to the immune response. On the contrary, the commonly used anti-COVID-19 vaccines generate protective humoral and cellular immunity. The magnitude of this immunity and the components involved in it are discussed in detail. Furthermore, many of the adverse effects of these vaccines can be explained on the basis of immune reactions against the different components of the vaccines. Regarding the appropriate choice of vaccine for different age groups, many factors have to be considered. This is a cornerstone, particularly in the following age groups: 1 day to 5 years, 6 to 11 years, and 12 to 17 years. Many factors are involved in deciding the route, doses, and schedule of vaccination for children. Another important issue in this dilemma is the hesitancy of families in making the decision about whether to vaccinate their children. Added to these difficulties is the choice by health authorities and governments concerning whether to make children's vaccination compulsory. In this respect, although rare and limited, adverse effects of vaccines in children have been detected, some of which, unfortunately, have been serious or even fatal. However, to achieve comprehensive control over COVID-19 in communities, both children and adults have to be vaccinated, as the former group represents a reservoir for viral transmission. The understanding of the various immunological mechanisms involved in SARS-CoV-2 infection and in the preparation and application of its vaccines has given the sciences a great opportunity to further deepen and expand immunological knowledge. This will hopefully be reflected positively on other diseases through gaining an immunological background that may aid in diagnosis and therapy. Humanity is still in continuous conflict with SARS-CoV-2 infection and will be for a while, but the future is expected to be in favor of the prevention and control of this disease.

Immune Response to SARS-CoV-2 Infections in Children with Secondary Immunodeficiencies

BACKGROUND AND PURPOSE

It is a matter of research, whether children with immunodeficiencies are able to generate an effective immune response to prevent SARS-CoV-2 reinfection. This study aimed to evaluate and compare the seroconversion rates and changes of lymphocyte subsets during COVID-19 in immunocompetent children and those with secondary immunodeficiencies.

METHODS

In 55 children - 28 immunocompromised and 27 immunocompetent - hospitalized with confirmed SARS-CoV-2 infection, the level of IgG antibodies against the Spike protein was determined on two to three occasions. In those children from the study group whose immunosuppressive treatment did not alter during the study (n = 13) and in selected children from the control group (n = 11), flow cytometric evaluation of lymphocyte subsets was performed twice - 2 weeks and 3 months post-infection.

RESULTS

Seroconversion reached 96.3% in both studied groups; however, the immunocompromised cohort achieved lower titers of detectable anti-S antibodies. There was no correlation between seroconversion or titers of antibodies and the total number of lymphocytes or their subsets. In the immunocompetent cohort, we reported a significant decrease in NK cells during the infection. In this group and the entire study population, a positive correlation was noticed between the CD4 + /CD8 + T cell ratio and the severity of COVID-19 pneumonia.

CONCLUSIONS

Children with secondary immunodeficiencies seroconvert in equal percentages but with a significantly lower titer of anti-S antibodies compared to their immunocompetent peers. The lower number of NK cells in the immunocompetent cohort may result from their participation in antiviral immunity, whereas reduced CD4 + /CD8 + T cell ratios among immunocompromised children may be a protective factor against a severe COVID-19.

Distinct Immune Phenotypes and Cytokine Profiles in Children with Differing Severity of COVID-19

BACKGROUND

Coronavirus disease 2019 (COVID-19) is usually mild and self-limited in children. However, a few Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infections in children may progress to severe disease with respiratory distress or can result in a multisystem inflammatory syndrome (MIS-C) associated with COVID-19. The immune mechanisms for these differential clinical outcomes are largely unknown.

METHODS

A prospective cohort study was performed to analyze the laboratory parameters, antibody response, immune phenotypes and cytokine profiles of 51 children with different clinical presentations of COVID-19.

RESULTS

We found that the absolute lymphocyte counts gradually decreased with disease severity. Furthermore, SARS-CoV-2 IgG levels in the acute phase and convalescence were not significantly different in patients with different disease severity. A decrease in CD3 + , CD4 + and CD8 + T cells was observed as disease severity increased. Both CD4 + and CD8 + T cells were activated in children with COVID-19, but no difference in the percentage of HLADR + -expressing cells was detected across the severity groups. In contrast, MIS-C patients exhibited augmented exhausted effector memory CD8 + T cells. Interestingly, the cytokine profile in sera of moderate/severe and MIS-C patients revealed an increase in anti-inflammatory IL-1RA and a suppression of tumor necrosis factor-α, RANTES, eotaxin and PDGF-BB. MIS-C patients also exhibited augmented IL-1β.

CONCLUSIONS

We report distinct immune profiles dependent on severity in pediatric COVID-19 patients. Further investigation in a larger population will help unravel the immune mechanisms underlying pediatric COVID-19.

SARS-CoV-2 Variant-Specific Infectivity and Immune Profiles Are Detectable in a Humanized Lung Mouse Model

Small animal models that accurately model pathogenesis of SARS-CoV-2 variants are required for ongoing research efforts. We modified our human immune system mouse model to support replication of SARS-CoV-2 by implantation of human lung tissue into the mice to create TKO-BLT-Lung (L) mice and compared infection with two different variants in a humanized lung model. Infection of TKO-BLT-L mice with SARS-CoV-2 recapitulated the higher infectivity of the B.1.1.7 variant with more animals becoming infected and higher sustained viral loads compared to mice challenged with an early B lineage (614D) virus. Viral lesions were observed in lung organoids but no differences were detected between the viral variants as expected. Partially overlapping but distinct immune profiles were also observed between the variants with a greater Th1 profile in VIDO-01 and greater Th2 profile in B.1.1.7 infection. Overall, the TKO-BLT-L mouse supported SARS-CoV-2 infection, recapitulated key known similarities and differences in infectivity and pathogenesis as well as revealing previously unreported differences in immune responses between the two viral variants. Thus, the TKO-BLT-L model may serve as a useful animal model to study the immunopathobiology of newly emerging variants in the context of genuine human lung tissue and immune cells.

SARS-CoV-2 herd immunity of the Kyrgyz population in 2021

In the fight against coronavirus infection, control of the immune response is of decisive importance, an important component of which is the seroprevalence of antibodies to SARS-CoV-2. Immunity to SARS-CoV-2 is formed either naturally or artificially through vaccination. The purpose of this study was to assess the seroprevalence of antibodies to SARS-CoV-2 in the population of Kyrgyzstan. A cross-sectional randomized study of seroprevalence was carried out according to a program developed by Rospotrebnadzor and the St. Petersburg Pasteur Institute, taking into account WHO recommendations. The ethics committees of the Association of Preventive Medicine (Kyrgyzstan) and the St. Petersburg Pasteur Institute (Russia) approved the study. Volunteers (9471) were recruited, representing 0.15% (95% CI 0.14-0.15) of the total population, randomized by age and region. Plasma antibodies (Abs) to the nucleocapsid antigen (Nag) were determined. In vaccinated individuals, Abs to the SARS-CoV-2 receptor-binding domain antigen (RBDag) were determined. Differences were considered statistically significant at p < 0.05. The SARS-CoV-2 Nag Ab seroprevalence was 48.7% (95% CI 47.7-49.7), with a maximum in the 60-69 age group [59.2% (95% CI 56.6-61.7)] and a minimum in group 1-17 years old [32.7% (95 CI: 29.4-36.1)]. The highest proportion of seropositive individuals was in the Naryn region [53.3% (95% CI 49.8-56.8)]. The lowest share was in Osh City [38.1% (95% CI 32.6-43.9)]. The maximum SARS-CoV-2 Nag seropositivity was found in the health-care sector [57.1% (95% CI 55.4-58.8)]; the minimum was seen among artists [38.6% (95% CI 26.0-52.4)]. Asymptomatic SARS-CoV-2 Nag seropositivity was 77.1% (95% CI 75.6-78.5). Vaccination with Sputnik V or Sinopharm produced comparable Ab seroprevalence. SARS-CoV-2 Nag seropositivity in the Kyrgyz population was 48.75% (95% CI 47.7-49.7), with the mass vaccination campaign undoubtedly benefitting the overall situation.

Elevated Levels of Pleiotropic Interleukin-6 (IL-6) and Interleukin-10 (IL-10) are Critically Involved With the Severity and Mortality of COVID-19: An Updated Longitudinal Meta-Analysis and Systematic Review on 147 Studies

Objectives

Disruption in the natural immune reaction due to SARS-CoV-2 infection can initiate a potent cytokine storm among COVID-19 patients. An elevated level of IL-6 and IL-10 during a hyperinflammatory state plays a vital role in increasing the risk of severity and mortality. In this study, we aimed to evaluate the potential of circulating IL-6 and IL-10 levels as biomarkers for detecting the severity and mortality of COVID-19.

Methods

This study was conducted according to the Cochrane Handbook and PRISMA guidelines. Authorized databases were searched to extract suitable studies using specific search terms. RevMan 5.4 was applied for performing the meta-analysis. Mean differences in IL-6 and IL-10 levels were calculated among COVID-19 patients via a random-effects model. NOS scoring, publication bias and sensitivity analyses were checked to ensure study quality.

Results

A total of 147 studies were selected, with 31 909 COVID-19 patients under investigation. In the severity analysis, the mean concentration of IL-6 was significantly higher in the severe COVID-19 cases than in the non-severe cases (MD: 19.98; P < .001; 95% CI: 17.56, 22.40). Similar result was observed for IL-10 mean concentration in severe COVID-19 cases (MD: 1.35; P < .001; 95% CI: 0.90, 1.80). In terms of mortality analysis, circulating IL-6 showed sharp elevation in the deceased patients (MD: 42.11; P < .001; 95% CI: 36.86, 47.36). IL-10 mean concentration was higher in the dead patients than in the survived patients (MD: 4.79; P < .001; 95% CI: 2.83, 6.75). Publication bias was not found except for comparing IL-6 levels with disease severity. Sensitivity analysis also reported no significant deviation from the pooled outcomes.

Conclusions

Elevated levels of circulating IL-6 and IL-10 signifies worsening of COVID-19. To monitor the progression of SARS-CoV-2 infection, IL-6 and IL-10 should be considered as potential biomarkers for severity and mortality detection in COVID-19.

Systematic review registration

INPLASY registration number: INPLASY202240046.

HMGB1: A Potential Target of Nervus Vagus Stimulation in Pediatric SARS-CoV-2-Induced ALI/ARDS

From the start of pandemics, children were described as the ones who were less affected by SARS-Cov-2 or COVID-19, which was mild in most of the cases. However, with the growing vaccination rate of the adult population, children became more exposed to the virus and more cases of severe SARS-CoV-2-induced ARDS are being diagnosed with the disabling consequences or lethal outcomes associated with the cytokine storm. Thus, we do hypothesize that some of the children could benefit from nervus vagus stimulation during COVID-19 ARDS through the inhibition of HMGB1 release and interaction with the receptor, resulting in decreased neutrophil accumulation, oxidative stress, and coagulopathy as well as lung vascular permeability. Moreover, stimulation through alpha-7 nicotinic acetylcholine receptors could boost macrophage phagocytosis and increase the clearance of DAMPs and PAMPs. Further rise of FGF10 could contribute to lung stem cell proliferation and potential regeneration of the injured lung. However, this stimulation should be very specific, timely, and of proper duration, as it could lead to such adverse effects as increased viral spread and systemic infection, especially in small children or infants due to specific pediatric immunity state and anatomical features of the respiratory system.

Immunopathology of SARS-CoV-2 Infection: A Focus on T Regulatory and B Cell Responses in Children Compared with Adults

While the clinical impact of COVID-19 on adults has been massive, the majority of children develop pauci-symptomatic or even asymptomatic infection and only a minority of the latter develop a fatal outcome. The reasons of such differences are not yet established. We examined cytokines in sera and Th and B cell subpopulations in peripheral blood mononuclear cells (PBMC) from 40 children (<18 years old), evaluating the impact of COVID-19 infection during the pandemic’s first waves. We correlated our results with clinical symptoms and compared them to samples obtained from 16 infected adults and 7 healthy controls. While IL6 levels were lower in SARS-CoV-2+ children as compared to adult patients, the expression of other pro-inflammatory cytokines such as IFNγ and TNFα directly correlated with early age infection and symptoms. Th and B cell subsets were modified during pediatric infection differently with respect to adult patients and controls and within the pediatric group based on age. Low levels of IgD− CD27+ memory B cells correlated with absent/mild symptoms. On the contrary, high levels of FoxP3+/CD25high T-Regs associated with a moderate−severe clinical course in the childhood. These T and B cells subsets did not associate with severity in infected adults, with children showing a predominant expansion of immature B lymphocytes and natural regulatory T cells. This study shows differences in immunopathology of SARS-CoV-2 infection in children compared with adults. Moreover, these data could provide information that can drive vaccination endpoints for children.

Why Does the Severity of COVID-19 Differ With Age?: Understanding the Mechanisms Underlying the Age Gradient in Outcome Following SARS-CoV-2 Infection

Although there are many hypotheses for the age-related difference in the severity of COVID-19, differences in innate, adaptive and heterologous immunity, together with differences in endothelial and clotting function, are the most likely mechanisms underlying the marked age gradient. Children have a faster and stronger innate immune response to SARS-CoV-2, especially in the nasal mucosa, which rapidly controls the virus. In contrast, adults can have an overactive, dysregulated and less effective innate response that leads to uncontrolled pro-inflammatory cytokine production and tissue injury. More recent exposure to other viruses and routine vaccines in children might be associated with protective cross-reactive antibodies and T cells against SARS-CoV-2. There is less evidence to support other mechanisms that have been proposed to explain the age-related difference in outcome following SARS-CoV-2 infection, including pre-existing immunity from exposure to common circulating coronaviruses, differences in the distribution and expression of the entry receptors ACE2 and TMPRSS2, and difference in viral load.

The legacy of maternal SARS-CoV-2 infection on the immunology of the neonate

Despite extensive studies into severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the effect of maternal infection on the neonate is unclear. To investigate this, we characterized the immunology of neonates born to mothers with confirmed SARS-CoV-2 infection during pregnancy. Here we show that maternal SARS-CoV-2 infection affects the neonatal immune system. Despite similar proportions of B cells, CD4⁺ T cells and CD8⁺ T cells, increased percentages of natural killer cells, Vδ2⁺ γδ T cells and regulatory T cells were detected in neonates born to mothers with recent or ongoing infection compared with those born to recovered or uninfected mothers. Increased plasma cytokine levels were also evident in neonates and mothers within the recent or ongoing infection group. Cytokine functionality was enhanced in neonates born to SARS-CoV-2-exposed mothers, compared to those born to uninfected mothers. In most neonates, this immune imprinting was nonspecific, suggesting vertical transmission of SARS-CoV-2 is limited, a finding supported by a lack of SARS-CoV-2-specific IgM in neonates despite maternal IgG transfer.

Risk factors for poor prognosis in children and adolescents with COVID-19: A systematic review and meta-analysis

BACKGROUND

This study provides the first systematic review and meta-analysis to identify the predictors of unfavorable prognosis of COVID-19 in children and adolescents.

METHODS

We searched literature databases until July 2021 for studies that investigated risk factors for unfavorable prognosis of children and adolescents with COVID-19. We used random-effects models to estimate the effect size with 95% confidence interval (CI).

FINDINGS

We identified 56 studies comprising 79,104 individuals. Mortality was higher in patients with multisystem inflammatory syndrome (MIS-C) (odds ratio [OR]=58.00, 95% CI 6.39-526.79) and who were admitted to intensive care (OR=12.64, 95% CI 3.42-46.68). Acute respiratry distress syndrme (ARDS) (OR=29.54, 95% CI 12.69-68.78) and acute kidney injury (AKI) (OR=55.02, 95% CI 6.26-483.35) increased the odds to be admitted to intensive care; shortness of breath (OR=16.96, 95% CI 7.66-37.51) increased the need of respiratory support; and neurological diseases (OR=5.16, 95% CI 2.30-11.60), C-reactive protein (CRP) level ≥80 mg/L (OR=11.70, 95% CI 4.37-31.37) and D-dimer level ≥0.5ug/mL (OR=20.40, 95% CI 1.76-236.44) increased the odds of progression to severe or critical disease.

INTERPRETATION

Congenital heart disease, chronic pulmonary disease, neurological diseases, obesity, MIS-C, shortness of breath, ARDS, AKI, gastrointestinal symptoms, elevated CRP and D-dimer are associated with unfavourable prognosis in children and adolescents with COVID-19.

A poor and delayed anti-SARS-CoV2 IgG response is associated to severe COVID-19 in children

Background

Most children and youth develop mild or asymptomatic disease during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, a very small number of patients suffer severe Coronavirus induced disease 2019 (COVID-19). The reasons underlying these different outcomes remain unknown.

Methods

We analyzed three different cohorts: children with acute infection (n=550), convalescent children (n=138), and MIS-C (multisystem inflammatory syndrome in children, n=42). IgG and IgM antibodies to the spike protein of SARS-CoV-2, serum-neutralizing activity, plasma cytokine levels, and the frequency of circulating Follicular T helper cells (cTfh) and plasmablasts were analyzed by conventional methods.

Findings

Fifty-eight percent of the children in the acute phase of infection had no detectable antibodies at the time of sampling while a seronegative status was found in 25% and 12% of convalescent and MIS-C children, respectively. When children in the acute phase of the infection were stratified according disease severity, we found that contrasting with the response of children with asymptomatic, mild and moderate disease, children with severe COVID-19 did not develop any detectable response. A defective antibody response was also observed in the convalescent cohort for children with severe disease at the time of admission. This poor antibody response was associated to both, a low frequency of cTfh and a high plasma concentration of inflammatory cytokines.

Interpretation

A weak and delayed kinetic of antibody response to SARS-CoV-2 together with a systemic pro-inflammatory profile characterize pediatric severe COVID-19. Because comorbidities are highly prevalent in children with severe COVID-19, further studies are needed to clarify their contribution in the weak antibody response observed in severe disease.

Funding

National Agency for Scientific and Technological Promotion from Argentina (IP-COVID-19-0277 and PMO-BID-PICT2018-2548).

Pediatric COVID-19: Immunopathogenesis, Transmission and Prevention

Children are unique in the context of the COVID-19 pandemic. Overall, SARS-CoV-2 has a lower medical impact in children as compared to adults. A higher proportion of children than adults remain asymptomatic following SARS-CoV-2 infection and severe disease and death are also less common. This relative resistance contrasts with the high susceptibility of children to other respiratory tract infections. The mechanisms involved remain incompletely understood but could include the rapid development of a robust innate immune response. On the other hand, children develop a unique and severe complication, named multisystem inflammatory syndrome in children, several weeks after the onset of symptoms. Although children play an important role in the transmission of many pathogens, their contribution to the transmission of SARS-CoV-2 appears lower than that of adults. These unique aspects of COVID-19 in children must be considered in the benefit-risk analysis of vaccination. Several COVID-19 vaccines have been authorized for emergency use in adolescents and clinical studies are ongoing in children. As the vaccination of adolescents is rolled out in several countries, we shall learn about the impact of this strategy on the health of children and on transmission within communities.