SARS-CoV-2 mRNA Vaccine Elicits Sustained T Cell Responses Against the Omicron Variant in Adolescents.

Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been acknowledged as an effective mean of preventing infection and hospitalization. However, the emergence of highly transmissible SARS-CoV-2 variants of concern (VOCs) has led to substantial increase in infections among children and adolescents. Vaccine-induced immunity and longevity have not been well defined in this population.

Distinct Clinical and Laboratory Features of COVID-19 in Children During the Pre-Delta, Delta and Omicron Wave.

Background: The SARS-CoV-2 variants of concern exhibit distinct features in terms of transmissibility and virulence. This study compared the clinical characteristics of COVID-19 in children during pre-Delta, Delta and Omicron waves.

Methods: Medical records of 1163 children <19 years of age with COVID-19 admitted to a designated hospital in Seoul, South Korea, were analyzed.

Croup as a Manifestation of SARS-CoV-2 Omicron Variant Infection in Young Children.

Croup is an acute upper respiratory disease primarily caused by the parainfluenza virus. Owing to inflammation and edema of the upper airways, children present with barky cough and stridor, and some may experience respiratory distress. We investigated children aged < 5 years with coronavirus disease 2019 (COVID-19) admitted to two hospitals in Seoul, South Korea, and observed a spike in croup cases during the omicron surge.

Antibody Responses to SARS-CoV-2 in Children With COVID-19.

Background: The immunologic features of children with coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are not clearly delineated. This study was conducted to evaluate SARS-CoV-2-specific antibody responses in children with COVID-19.

Methods: The levels of anti-spike (S) IgG, anti-SARS-CoV-2 IgG, and neutralizing antibody (NAb) were measured during various time points in children <19 years of age with COVID-19 in South Korea from February 2020 to September 2020.

Waning Effectiveness of One-dose Universal Varicella Vaccination in Korea, 2011-2018: a Propensity Score Matched National Population Cohort.

Background: Despite high coverage (~98%) of universal varicella vaccination (UVV) in the Republic of Korea since 2005, reduction in the incidence rate of varicella is not obvious. The study aimed to evaluate the vaccine effectiveness (VE) of one-dose UVV by timeline and severity of the disease.

Methods: All children born in Korea in 2011 were included for this retrospective cohort study that analyzed insurance claims data from 2011-2018 and the varicella vaccination records in the immunization registry.

Trend change of nasopharyngeal colonization with Streptococcus pneumoniae and non-typeable Haemophilus influenzae in children attending daycare centres: nationwide population-based study, South Korea 2014 and 2019.

Background: Nasopharyngeal (NP) colonization with Streptococcus pneumoniae and non-typeable Haemophilus influenzae (NTHi) is common in children, and may evolve as the source of invasive infections. In Korea, the pneumococcal conjugate vaccines (PCVs) were introduced >10 years ago, enabling the authors to study the effect of the vaccine in preventing carriage.

Methods: NP swabs were taken and a household survey was conducted at daycare centres located in different regions of Korea in 2014 and 2019.

Persistent high macrolide resistance rate and increase of macrolide-resistant ST14 strains among Mycoplasma pneumoniae in South Korea, 2019-2020.

Background: Expansion of the single sequence type 3 (ST3) was associated with a high macrolide resistance rate among Mycoplasma pneumoniae in Korea during the 2014-2016 epidemic. This study investigates the macrolide resistance rate and genetic diversity of the subsequent epidemic of M. pneumoniae pneumonia in 2019-2020.

Clinical Efficacy of Doxycycline for Treatment of Macrolide-Resistant Pneumonia in Children.

In areas with high prevalence of macrolide-resistant (MRMP) pneumonia, treatment in children has become challenging. This study aimed to analyze the efficacy of macrolides and doxycycline with regard to the presence of macrolide resistance. We analyzed children with MP pneumonia during the two recent epidemics of 2014-2015 and 2019-2020 from four hospitals in Korea.

Limited Benefit of Facility Isolation and the Rationale for Home Care in Children with Mild COVID-19.

Considering the mild degree of coronavirus disease 2019 (COVID-19) in children and the enormous stress caused by isolation in unfamiliar places, policies requiring mandatory isolation at medical facilities should be reevaluated especially given the impact of the pandemic on the availability of hospital beds. In this study, we assessed the usefulness of facility isolation and the transmissibility of severe acute respiratory syndrome coronavirus 2 by infected children to uninfected caregivers in isolation units at a hospital and a residential treatment center in Seoul during August-November 2020. Fifty-three children were included and median age was 4 years (range, 0-18).

Absence of SARS-CoV-2 Transmission from Children in Isolation to Guardians, South Korea.

We explored transmission of severe acute respiratory syndrome coronavirus 2 among 12 children and their uninfected guardians in hospital isolation rooms in South Korea. We found that, even with close frequent contact, guardians who used appropriate personal protective equipment were not infected by children with diagnosed coronavirus disease.

COVID-19 in children across three Asian cosmopolitan regions.

As another wave of COVID-19 outbreak has approached in July 2020, a larger scale COVID-19 pediatric Asian cohort summarizing the clinical observations is warranted. Children confirmed with COVID-19 infection from the Republic of Korea, the Hong Kong Special Administrative Region (HKSAR) and Wuhan, China, during their first waves of local outbreaks were included. Their clinical characteristics and the temporal sequences of the first waves of local paediatric outbreaks were compared.

Effects of Storage Temperature and Media/Buffer for SARS-CoV-2 Nucleic Acid Detection.

Objectives: The increase in the number of patients with coronavirus disease 2019 (COVID-19) has delayed real-time reverse transcription-quantitative polymerase chain reaction (RT-qPCR), requiring proper shipping and storage conditions, especially in hot weather. This study aims to assess how some conditions, such as storage period, temperature, media or buffer, and sample types, affect the results of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RT-qPCR.

Methods: SARS-CoV-2-positive specimens were collected from Boramae Medical Center for 2 months (from May to June 2020) and stored in different media or buffers at different temperatures.

Changes in the Etiology and Clinical Characteristics of Pediatric Infective Endocarditis in South Korea.

Objective: Changes in the epidemiology, clinical manifestations, and outcomes of infective endocarditis (IE) have been reported in recent years. This study was performed to analyze changing trends in the etiology of IE in children in South Korea.

Study Design: A retrospective study of children with IE was conducted from 2 hospitals in Korea from 2004 to 2019.

Clinical Characteristics and Viral RNA Detection in Children With Coronavirus Disease 2019 in the Republic of Korea.

Importance: There is limited information describing the full spectrum of coronavirus disease 2019 (COVID-19) and the duration of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA detection in children.

Objective: To analyze the full clinical course and the duration of SARS-CoV-2 RNA detectability in children confirmed with COVID-19 in the Republic of Korea, where rigorous public health interventions have been implemented.

Design, Setting, And Participants: This case series of children with COVID-19 was conducted in 20 hospitals and 2 nonhospital isolation facilities across the country from February 18, 2020, to March 31, 2020.

Role of children in household transmission of COVID-19.

Objective: Transmissibility of COVID-19 by children in the household is not clear. Herein, we describe children's role in household transmission of COVID-19.

Design And Setting: All paediatric COVID-19 index cases and their household members reported from 20 January to 6 April 2020 in South Korea were reviewed.

Effectiveness of trivalent inactivated influenza vaccines in children during 2017-2018 season in Korea: Comparison of test-negative analysis by rapid and RT-PCR influenza tests.

Objectives: In Korea, the National Immunization Program provided trivalent inactivated influenza vaccines (IIV3) to all children aged 6-59 months during the 2017-2018 season. In this study, we aimed to evaluate the vaccine effectiveness (VE) of IIV3 in children during the 2017-2018 season.

Methods: Children aged 6-59 months who were tested for influenza for their acute respiratory illness in four hospitals during the 2017-2018 influenza season were included.

Viral RNA Load in Mildly Symptomatic and Asymptomatic Children with COVID-19, Seoul, South Korea.

Along with positive SARS-CoV-2 RNA in nasopharyngeal swabs, viral RNA was detectable at high concentration for >3 weeks in fecal samples from 12 mildly symptomatic and asymptomatic children with COVID-19 in Seoul, South Korea. Saliva also tested positive during the early phase of infection. If proven infectious, feces and saliva could serve as transmission sources.

Abiotrophia defectiva as a cause of infective endocarditis with embolic complications in children.

Abiotrophia defectiva is a rare pathogen of infective endocarditis (IE) but is frequently involved in embolic complication and valvular dysfunction. IE caused by A. defectiva in children is poorly studied.

Sequential Analysis of Viral Load in a Neonate and Her Mother Infected With Severe Acute Respiratory Syndrome Coronavirus 2.

We report changes in viral load over time in a 27-day-old neonate with coronavirus disease 2019 who presented with fever, cough, and vomiting. Severe acute respiratory syndrome coronavirus 2 RNA was detected in the nasopharynx, oropharynx, stool, saliva, plasma, and urine. The highest viral RNA copies in nasopharynx decreased over time while viral load in stool remained high.

First Pediatric Case of Coronavirus Disease 2019 in Korea.

The large outbreak of coronavirus disease 2019 (COVID-19) that started in Wuhan, China has now spread to many countries worldwide. Current epidemiologic knowledge suggests that relatively few cases are seen among children, which limits opportunities to address pediatric specific issues on infection control and the children's contribution to viral spread in the community. Here, we report the first pediatric case of COVID-19 in Korea.

Cytomegalovirus disease in a retinoblastoma cohort: The role of preemptive screening.

Background: Cytomegalovirus (CMV) disease is underrecognized in children with retinoblastoma. This study investigated rates of CMV infection and disease in this specific population receiving chemotherapy.

Methods: From a cohort of 164 patients with retinoblastoma diagnosed from 2011 to 2018, 107 patients were evaluated for CMV infection determined by antigenemia assay or real-time PCR.

Comparative genomics of Mycoplasma pneumoniae isolated from children with pneumonia: South Korea, 2010-2016.

Background: Mycoplasma pneumoniae is a common cause of respiratory tract infections in children and adults. This study applied high-throughput whole genome sequencing (WGS) technologies to analyze the genomes of 30 M. pneumoniae strains isolated from children with pneumonia in South Korea during the two epidemics from 2010 to 2016 in comparison with a global collection of 48 M.