Omicron variant susceptibility to neutralizing antibodies induced in children by natural SARS-CoV-2 infection or COVID-19 vaccine.

The novel SARS-CoV-2 Omicron variant may increase the risk of re-infection and vaccine breakthrough infections as it possesses key mutations in the spike protein that affect neutralizing antibody response. Most studies on neutralization susceptibility were conducted using specimens from adult COVID-19 patients or vaccine recipients. However, since the paediatric population has an antibody response to SARS-CoV-2 infection that is distinct from the adult population, it is critical to assess the neutralization susceptibility of pediatric serum specimens. This study compared the neutralization susceptibility of serum specimens collected from 49 individuals of <18 years old, including 34 adolescent BNT162b2 (Pfizer-BioNTech) vaccine recipients, and 15 recovered COVID-19 patients aged between 2 and 17. We demonstrated that only 38.2% of BNT162b2 vaccine recipients and 26.7% of recovered COVID-19 patients had their serum neutralization titre at or above the detection threshold in our live virus microneutralization assay. Furthermore, the neutralizing antibody titer against the Omicron variant was substantially lower than those against the ancestral virus or the Beta variant. Our results suggest that vaccine recipients and COVID-19 patients in the pediatric age group will likely be more susceptible to vaccine breakthrough infections or reinfections due to the Omicron variant than previous variants.

Clinical Characteristics and Transmission of COVID-19 in Children and Youths During 3 Waves of Outbreaks in Hong Kong.

Importance: Schools were closed intermittently across Hong Kong to control the COVID-19 outbreak, which led to significant physical and psychosocial problems among children and youths. Objective: To compare the clinical characteristics and sources of infection among children and youths with COVID-19 during the 3 waves of outbreaks in Hong Kong in 2020. Design, Setting, and Participants: This cross-sectional study involved children and youths aged 18 years or younger with COVID-19 in the 3 waves of outbreaks from January 23 through December 2, 2020. Data were analyzed from December 2020 through January 2021. Main Outcomes and Measures: Demographic characteristics, travel and contact histories, lengths of hospital stay, and symptoms were captured through the central electronic database. Individuals who were infected without recent international travel were defined as having domestic infections. Results: Among 397 children and youths confirmed with COVID-19 infections, the mean (SD) age was 9.95 (5.34) years, 220 individuals (55.4%) were male, and 154 individuals (38.8%) were asymptomatic. There were significantly more individuals who were infected without symptoms in the second wave (59 of 118 individuals [50.0%]) and third wave (94 of 265 individuals [35.5%]) than in the first wave (1 of 14 individuals [7.1%]) (P = .001). Significantly fewer individuals who were infected in the second and third waves, compared with the first wave, had fever (first wave: 10 individuals [71.4%]; second wave: 22 individuals [18.5%]; third wave: 98 individuals [37.0%]; P < .001) or cough (first wave: 6 individuals [42.9%]; second wave: 15 individuals [12.7%]; third wave: 52 individuals [19.6%]; P = .02). Among all individuals, 394 individuals (99.2%) had mild illness. One patient developed chilblains (ie, COVID toes), 1 patient developed multisystem inflammatory syndrome in children, and 1 patient developed post-COVID-19 autoimmune hemolytic anemia. In all 3 waves, 204 patients with COVID-19 (51.4%) had domestic infections. Among these individuals, 186 (91.2%) reported having a contact history with another individual with COVID-19, of which most (183 individuals [90.0%]) were family members. In the third wave, 18 individuals with domestic infections had unknown contact histories. Three schoolmates were confirmed with COVID-19 on the same day and were reported to be close contacts. Conclusions and Relevance: This cross-sectional study found that nearly all children and youths with COVID-19 in Hong Kong had mild illness. These findings suggest that household transmission was the main source of infection for children and youths with domestic infections and that the risk of being infected at school was small.

COVID-19 in children across three Asian cosmopolitan regions.

ABSTRACT 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. Four hundred and twenty three children with COVID-19 were analyzed. Wuhan had the earliest peak, followed by Korea and HKSAR. Compared with Korea and Wuhan, patients in HKSAR were significantly older (mean age: 12.9 vs. 10.8 vs. 6.6 years, p < 0.001, respectively) and had more imported cases (87.5% vs. 16.5% vs. 0%, p < 0.001, respectively). The imported cases were also older (13.4 vs. 7.6 years, p < 0.001). More cases in HKSAR were asymptomatic compared to Korea and Wuhan (45.5% vs. 22.0% vs. 20.9%, p < 0.001, respectively), and significantly more patients from Wuhan developed fever (40.6% vs. 29.7% vs. 21.6%, p=0.003, respectively). There were significantly less imported cases than domestic cases developing fever after adjusting for age and region of origin (p = 0.046). 5.4% to 10.8% of patients reported anosmia and ageusia. None developed pediatric multisystem inflammatory syndrome temporally associated with SARS-CoV-2 (PMIS-TS). In general, adolescents were more likely to be asymptomatic and less likely to develop fever, but required longer hospital stays. In conclusion, majority patients in this pediatric Asian cohort had a mild disease. None developed PIMS-TS. Their clinical characteristics were influenced by travel history and age.

Determinants for asthma control, quality of life and use of complementary and alternative medicine in asthmatic pediatric patients in four cities.

BACKGROUND: Asthma is a significant chronic health problem worldwide. Management aims at disease control by reducing functional impairment and exacerbations and improving quality of life (QoL). We report a multi-center study to survey asthma control and QoL in four cities in the Pearl River Delta. METHODS: The conjoint survey involved ten Hong Kong pediatric hospitals/units, two Shenzhen hospitals, two Macau hospitals, and two Guangzhou hospitals on asthma control (using Asthma Control Test) and QoL (Pediatric Allergic Disease Quality of Life Questionnaire, PADQLQ). Acceptability of a treatment is graded as very good/good/fair/poor. RESULTS: Good asthma control was only reported in 80% subjects in Hong Kong, but higher in sister cities (85-94%, P < 0.001). Allergic rhinitis, "incense burning", and "smoker in family" were prevalent among the four cities. Logistic regression showed better control of asthma was associated with better PADQLQ (B = - 0.029, P < 0.001), better acceptability of bronchodilator (B = - 1.488, P = 0.025), negatively with "smoker in family" (B = - 0.83, P = 0.015) and various PADQLQ domains. Conversely, worse PADQLQ was associated with allergic rhinitis severity (B = 4.77, P < 0.001), poor control of asthma (B = 7.56, P < 0.001), increased frequency of traditional Chinese medicine use (B = 1.7, P < 0.05), increased frequency of bronchodilator usage (B = 1.05, P < 0.05), "smoker in family" (B = 4.05, P < 0.05), and incense burning at home (B = 3.9, P < 0.05). CONCLUSIONS: There are some clinical and cultural differences among the four southern Chinese cities within the Guangdong province. This study identifies potentially modifiable environmental and treatment factors associated with poor asthma control and QoL for health-care interventions. Having a smoker in the family is independently associated with poor asthma control and QoL.

DNA-based subtyping of glycogen storage disease type III: mutation and haplotype analysis of the AGL gene in Chinese.

Glycogen storage disease type III (GSD III) is an inborn error of glycogen metabolism caused by a deficiency of glycogen debranching enzyme (AGL). Here, we investigate two unrelated Hong Kong Chinese GSD III patients and identify a novel 5-base pair deletional mutation, 2715_2719delTCAGAin exon 22, in one patient and a nonsense mutation, 1222C>T (R408X) in exon 11, in another patient. Since GSD IIIb is only caused by mutation in exon 3 of the AGL gene, we diagnose our patients to have GSD IIIa, which is consistent with the clinical diagnosis. Until now, R408X has only been reported in Faroe Islands GSDIII patients and was thought to demonstrate a founder effect. In this study, haplotyping of the disease-bearing chromosomes in the AGL locus by 19 intragenic single nucleotide polymorphisms shows that R408X is linked with IVS16+8T and IVS23-21T in our patient while R408X is linked with IVS16+8C and IVS23-21A in the Faroe Islands. The different haplotypes of R408X in Chinese and Faroese indicated that R408X is a recurrent mutation.