Physical Fitness and Body Mass Index Status of Hong Kong Primary Schoolchildren across the COVID-19 Pandemic, before and after School Closure.

OBJECTIVE: To determine whether health-related physical fitness and body mass index (BMI) status differed before and after school closure from the COVID-19 pandemic in a population-based cohort of Hong Kong primary schoolchildren. STUDY DESIGN: We examined the BMI z score, BMI status, and physical fitness z scores including (i) upper limb muscle strength, (ii) 1-minute sit-up test, (iii) sit-and-reach test, and (iv) endurance run tests, among 3 epochs: prepandemic (September 2018-August 2019), before school closure (September 2019-January 2020), and partial school reopening (September 2021-August 2022), using a repeated cross-sectional approach. RESULTS: A total of 137 752 primary schoolchildren aged 6-12 years were recruited over 3 academic years. Obesity increased significantly from 25.9% in 2018/19 to 31.0% in 2021/22, while underweight increased slightly from 6.1% to 6.5%. All tested parameters were adversely affected by the pandemic. The negative trend over time was far more pronounced in all 4 physical fitness scores in the underweight group, although performance in handgrip strength had no significance between 2018/19 and 2021/22. CONCLUSIONS: Schoolchildren who are both underweight and overweight/obese are vulnerable to adverse changes in physical fitness during the COVID-19 pandemic. To eliminate the negative health and fitness outcomes, it is urgent to develop strategies for assisting schoolchildren in achieving a healthy weight, especially in the postpandemic era.

Differential patterns of fish sensitization in Asian populations: Implication for precision diagnosis.

BACKGROUND: The current diagnostics of fish allergy lack sufficient accuracy such that more reliable tests such as component-resolved diagnosis (CRD) are urgently needed. This study aimed at identifying fish allergens of salmon and grass carp and evaluating the sensitization pattern in fish allergic subjects from two distinct populations in Asia. METHODS: One hundred and three fish allergic subjects were recruited from Hong Kong (67 subjects) and Japan (46 subjects). Western blot and mass spectrometry were used to identify allergens from salmon and grass carp. Fish allergens were purified and tested against 96 sera on ELISA to analyze patients' sensitization pattern. The protein profiles of salmon meat prepared under different cooking methods until core temperature reached 80 °C were evaluated by SDS-PAGE and mass spectrometry. RESULTS: Three common allergens between salmon and grass carp, namely enolase, glycerldehyde-3-phosphate dehydrogenase (GAPDH) and parvalbumin, and two salmon-specific allergens collagen and aldolase were identified. Parvalbumin was the major allergen for both fishes showing an overall sensitization rate of 74.7%, followed by collagen (38.9%), aldolase (38.5%) and enolase (17.8%). Japanese subjects showed more diverse allergen sensitization pattern and more frequent IgE-binding to heat-labile salmon allergens. Compared with steaming and boiling, cooking by baking and frying retained more fish proteins inclusive of heat-labile allergens. CONCLUSIONS: Fish allergic patients from different Asian populations show varying fish allergen sensitization profiles. The relevant extracts and components for diagnosis are population-dependent but parvalbumin and collagen are important biomarkers. Cooking methods modify allergen composition of salmon and appear to influence patients' allergic manifestations.

Comprehending the allergen repertoire of shrimp for precision molecular diagnosis of shrimp allergy.

BACKGROUND: Clinical management of shrimp allergy is hampered by the lack of accurate tests. Molecular diagnosis has been shown to more accurately reflect the clinical reactivity but the full spectrum of shrimp allergens and their clinical relevance are yet to be established. We therefore sought to comprehend the allergen repertoire of shrimp, investigate and compare the sensitization pattern and diagnostic value of the allergens in allergic subjects of two distinct populations. METHODS: Sera were collected from 85 subjects with challenge-proven or doctor-diagnosed shrimp allergy in Hong Kong and Thailand. The IgE-binding proteins of Penaeus monodon were probed by Western blotting and identified by mass spectrometry. Recombinant shrimp allergens were synthesized and analyzed for IgE sensitization by ELISA. RESULTS: Ten IgE-binding proteins were identified, and a comprehensive panel of 11 recombinant shrimp allergens was generated. The major shrimp allergens among Hong Kong subjects were troponin C (Pen m 6) and glycogen phosphorylase (Pen m 14, 47.1%), tropomyosin (Pen m 1, 41.2%) and sarcoplasmic-calcium binding protein (Pen m 4, 35.3%), while those among Thai subjects were Pen m 1 (68.8%), Pen m 6 (50.0%) and fatty acid-binding protein (Pen m 13, 37.5%). Component-based tests yielded significantly higher area under curve values (0.77-0.96) than shrimp extract-IgE test (0.70-0.75). Yet the best component test differed between populations; Pen m 1-IgE test added diagnostic value only in the Thai cohort, whereas sensitizations to other components were better predictors of shrimp allergy in Hong Kong patients. CONCLUSION: Pen m 14 was identified as a novel shrimp allergen predictive of challenge outcome. Molecular diagnosis better predicts shrimp allergy than conventional tests, but the relevant component is population dependent.

Changing pattern of pediatric anaphylaxis in Hong Kong, 2010-2019.

BACKGROUND: Anaphylaxis is a significant health burden in most Western countries, but there are little published data on the incidence and pattern of anaphylaxis in Asia. We aim to determine the incidence rate and pattern of anaphylaxis over the past decade among the pediatric population in Hong Kong. METHODS: Medical records of patients presenting with allergy-related symptoms during the period 2010 to 2019 were examined. Pediatric patients aged below 18 years who fulfilled the diagnostic criteria for anaphylaxis laid out by the NIAID/FAAN were analyzed. Incidence rates were calculated using population statistics as the denominator. All information pertaining to the anaphylaxis events and patients' characteristics was retrieved using standardized data collection forms. RESULTS: The overall 10-year estimated incidence of anaphylaxis was 9.76 per 100,000 person-years, with a rising trend of anaphylaxis incidence across time. Food-induced anaphylaxis accounted for the majority of hospital presentations, of which peanut and shellfish were the top food triggers in our population. Majority of anaphylaxis episodes were of Grade 4 severity, and young age was a significant predictor of severe allergic reactions. Half of the anaphylaxis episodes were misdiagnosed and adrenaline was only utilized in 42.2% of cases, of which 9.4% were administered adrenaline prior to hospital arrival. CONCLUSIONS: An increasing trend of anaphylaxis incidence over the past decade is evident in Hong Kong children, with a discrepantly low accuracy in diagnosis and suboptimal management of anaphylaxis. There is a pressing need to heighten public and physicians' awareness of the distinctive features of anaphylaxis in the pediatric age-group.

Vulnerability and resilience in children during the COVID-19 pandemic.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic is having a profound impact on the health and development of children worldwide. There is limited evidence on the impact of COVID-19 and its related school closures and disease-containment measures on the psychosocial wellbeing of children; little research has been done on the characteristics of vulnerable groups and factors that promote resilience. METHODS: We conducted a large-scale cross-sectional population study of Hong Kong families with children aged 2-12 years. Parents completed an online survey on family demographics, child psychosocial wellbeing, functioning and lifestyle habits, parent-child interactions, and parental stress during school closures due to COVID-19. We used simple and multiple linear regression analyses to explore factors associated with child psychosocial problems and parental stress during the pandemic. RESULTS: The study included 29,202 individual families; of which 12,163 had children aged 2-5 years and 17,029 had children aged 6-12 years. The risk of child psychosocial problems was higher in children with special educational needs, and/or acute or chronic disease, mothers with mental illness, single-parent families, and low-income families. Delayed bedtime and/or inadequate sleep or exercise duration, extended use of electronic devices were associated with significantly higher parental stress and more psychosocial problems among pre-schoolers. CONCLUSIONS: This study identifies vulnerable groups of children and highlights the importance of strengthening family coherence, adequate sleep and exercise, and responsible use of electronic devices in promoting psychosocial wellbeing during the COVID-19 pandemic.

Comorbidity of ADHD and allergic diseases in early adolescence: The role of parental smoking at home.

A growing body of research suggests an association between attention deficit hyperactivity disorder (ADHD) and allergic disorders, but little work has been done to explore the role of external factors such as parental smoking at home in the development of comorbid ADHD and allergic disorders. This study aimed to examine the association between allergic diseases and ADHD adjusted for exposure to parental smoking at home in early adolescents. We recruited 250 male (41.7%) and 350 female (58.3%) adolescents (mean [SD] age, 13.29 [0.52] years) via chain-referral sampling. Their ADHD symptoms were assessed by the parent proxy-report version of the Chinese Strengths and Weaknesses of Attention-Deficit/Hyperactivity-symptoms and Normal-behaviours (SWAN) rating scale. Data on the participants' history of clinician-diagnosed allergic diseases, family socio-demographics, and parental smoking habit were collected using a parent-completed questionnaire. Regression analyses were performed to examine the associations of interest. The levels of ADHD symptoms were comparable between allergic and non-allergic participants after controlling for child and family demographics and parental smoking at home. Notably, the risk of probable ADHD was particularly high in participants with food allergies (odd ratio = 4.51, p = 0.011) but not in those with allergic rhinitis after adjusting for parental smoking at home. Our findings suggest that second-hand smoke exposure at home is a potential risk factor underlying the link between ADHD and allergic diseases. Current management guidelines should emphasize the importance of early identification and cessation of tobacco smoke exposure for prevention of comorbidity of ADHD and allergic disorders. Clinical Trial Registration (if any): NA.

Effectiveness of Partial and Full Influenza Vaccination Among Children Aged <9 Years in Hong Kong, 2011-2019.

BACKGROUND: Two doses of influenza vaccination are recommended for previously unvaccinated children aged <9 years, and receipt of 1 dose is sometimes termed "partial vaccination." We assessed the effectiveness of partial and full influenza vaccination in preventing influenza-associated hospitalization among children in Hong Kong. METHODS: Using the test-negative design we enrolled 23 187 children aged <9 years admitted to hospitals with acute respiratory illness from September 2011 through March 2019. Vaccination and influenza status were recorded. Fully vaccinated children included those vaccinated with 2 doses or, if previously vaccinated, those vaccinated with 1 dose. Partially vaccinated children included those who should have received 2 doses but only received 1 dose. We estimated vaccine effectiveness (VE) by using conditional logistic regression models matched on epidemiological week. RESULTS: Overall VE estimates among fully and partially vaccinated children were 73% (95% confidence interval, 69%-77%) and 31% (95% confidence interval, 8%-48%), respectively. A consistently higher VE was observed in children fully vaccinated against each influenza virus type/subtype. The effectiveness of partial vaccination did not vary by age group. CONCLUSIONS: Partial vaccination was significantly less effective than full vaccination. Our study supports the current recommendation of 2 doses of influenza vaccination in previously unvaccinated children <9 years of age.

Influenza Vaccine Effectiveness Against Influenza A(H3N2) Hospitalizations in Children in Hong Kong in a Prolonged Season, 2016/2017.

Background: Influenza A(H3N2) viruses circulated for 12 consecutive months in Hong Kong in 2016-2017, peaking in late June and July 2017. The objective of our study was to estimate the effectiveness of influenza vaccination in preventing hospitalizations in children in Hong Kong. Methods: We conducted a test-negative study between 1 September 2016 and 31 August 2017, enrolling children 6 months to 17 years of age hospitalized for an acute respiratory infection. Influenza was diagnosed by PCR on nasopharyngeal aspirates. Results: We enrolled 5514 children, including 3608 children 6 months to 2 years, 1600 children 3-5 years, and 1206 children 6-17 years of age. Influenza-associated hospitalizations occurred throughout the study year but time of vaccination of these children was also wide spread, from September 2016 to May 2017. Influenza vaccine effectiveness (VE) was 39.7% (95% confidence interval [CI], 14.7%-57.3%) against laboratory-confirmed influenza A(H3N2). In analyses stratified by time since vaccination, the VE against influenza A(H3N2) was 52.8% (95% CI, 17.1%-73.2%) within 3 months of vaccination, and 31.2% (95% CI, -6.6% to 55.6%) 4-6 months after vaccination. Conclusions: Influenza vaccination was effective in preventing hospitalizations in children in Hong Kong.

Interim estimate of influenza vaccine effectiveness in hospitalised children, Hong Kong, 2017/18.

We conducted a hospital-based test-negative study in Hong Kong to estimate influenza vaccine effectiveness (VE) for the winter of 2017/18. The interim analysis included data on 1,078 children admitted between 4 December 2017 and 31 January 2018 with febrile acute respiratory illness and tested for influenza. We estimated influenza VE at 66% (95% confidence interval (CI): 43-79) overall, and 65% (95% CI: 40-80) against influenza B, the dominant virus type (predominantly B/Yamagata).

Influenza vaccine effectiveness against hospitalizations associated with influenza A(H3N2) in Hong Kong children aged 9 months to 17 years, June-November 2023.

A test negative study was carried out from 13 June through to 15 November 2023 enrolling 3183 children hospitalized with acute respiratory illness in Hong Kong. Influenza A and B viruses were detected in 528 (16.6%) children, among which 419 (79.4%) were influenza A(H3N2). The overall vaccine effectiveness against hospitalization associated with any influenza virus infection was estimated as 22.4% (95% CI: -11.7%, 46.1%), and against influenza A(H3N2) specifically was 14.3% (95% CI: -29.2%, 43.2%). Despite the moderate to low VE estimated here, which could be a result of waning immunity and antigenic drift, influenza vaccination remains an important approach to reduce the impact of influenza in children.

Normative values of motor performance and their relationship with BMI status in Hong Kong preschoolers.

This study aimed to establish sex- and age-specific reference values for motor performance (MP) in Hong Kong preschoolers aged 3-5 years old and examine the relationship between MP and BMI status. A cross-sectional study was conducted among 5579 preschoolers in Hong Kong. Three MP tests were administered, and height and weight information were collected. GAMLSS was used to compute the normative values of the motor tests. Boys outperformed girls in activities requiring muscle strength and power, while girls outperformed boys in activities requiring balance and coordination. The MP scores increased with age for both overarm beanbag throw and standing long jump for both sexes, while the one-leg balance scores showed larger differences between P50 and P95 in older preschoolers. Children with excessive weight performed worse in standing long jump and one-leg balance compared to their healthy weight peers. This study provides valuable information on the MP of preschoolers in Hong Kong, including sex- and age-specific reference values and the association between BMI status and MP scores. These findings can serve as a reference for future studies and clinical practice and highlight the importance of promoting motor skill development in preschoolers, particularly those who are overweight or obese.

Real-World Sensitization and Tolerance Pattern to Seafood in Fish-Allergic Individuals.

BACKGROUND: Seafood is a common cause of food allergy and anaphylaxis, but there are limited published real-world data describing the clinical presentation of fish and shellfish allergies. OBJECTIVE: This study aimed to examine the clinical characteristics, immunological profile, and tolerance pattern to fish, crustaceans, and mollusks in fish-allergic individuals. METHODS: Patients presenting with IgE-mediated fish allergy between 2016 and 2021 were recruited. A comprehensive sensitization profile including specific IgE and skin prick test to various fish and shellfish species and a detailed clinical history including individuals' recent seafood consumption were evaluated. RESULTS: A total of 249 fish-allergic individuals (aged 4.2 ± 5.8 years) were recruited from 6 allergy clinics in Hong Kong, and they had experienced their fish-allergic reaction 2.2 ± 3.4 years before enrollment. Seventy-five subjects (30%) reacted to either grass carp, salmon, grouper, or cod in oral food challenges. We identified an IgE sensitization gradient that corresponded to the level of ß-parvalbumin in fish. In total, 40% of fish-allergic individuals reported tolerance to 1 or more types of fish, more commonly to fish with a lower ß-parvalbumin level such as tuna and salmon, compared with ß-parvalbumin-rich fish such as catfish and grass carp. Despite fish and shellfish cosensitization, 41% of individuals reported tolerance to crustaceans, mollusks, or both, whereas shellfish avoidance occurred in half of the fish-allergic individuals, of whom 33% lacked shellfish sensitization. CONCLUSIONS: Fish allergy commonly presents in early childhood. A considerable proportion of fish-allergic patients are selectively tolerant to certain fish, typically those with lower levels of ß-parvalbumin. There is an unmet need to promote precision medicine for seafood allergies.

Influenza Vaccine Effectiveness Against Influenza-Associated Hospitalization in Hong Kong Children Aged 9 Months to 17 Years, March-June 2023.

In March-June 2023, we conducted a test-negative study in 1671 children who were hospitalized with acute respiratory illness in Hong Kong. Two hundred and eighty-six children (17.2%) were tested positive for influenza virus including 188 with A(H1N1). We estimated influenza vaccine effectiveness against influenza-associated hospitalization as 69.6% (95% confidence interval: 49.3%, 81.7%).

Severity of SARS-CoV-2 Omicron BA.2 infection in unvaccinated hospitalized children: comparison to influenza and parainfluenza infections.

There has been a rapid surge of hospitalization due to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variants globally. The severity of Omicron BA.2 in unexposed, unvaccinated, hospitalized children is unknown. We investigated the severity and clinical outcomes of COVID-19 infection during the Omicron wave in uninfected, unvaccinated hospitalized children and in comparison with influenza and parainfluenza viral infections. This population-based study retrieved data from the HK territory-wide CDARS database of hospitalisations in all public hospitals and compared severe outcomes for the Omicron BA.2-dominant fifth wave (5-28 February 2022, n = 1144), and influenza and parainfluenza viruses (1 January 2015-31 December 2019, n = 32212 and n = 16423, respectively) in children 0-11 years old. Two deaths (0.2%) out of 1144 cases during the initial Omicron wave were recorded. Twenty-one (1.8%) required PICU admission, and the relative risk was higher for Omicron than influenza virus (n = 254, 0.8%, adjusted RR = 2.1, 95%CI 1.3-3.3, p = 0.001). The proportion with neurological complications was 15.0% (n = 171) for Omicron, which was higher than influenza and parainfluenza viruses (n = 2707, 8.4%, adjusted RR = 1.6, 95%CI 1.4-1.9 and n = 1258, 7.7%, adjusted RR = 1.9, 95%CI 1.6-2.2, p < 0.001 for both, respectively). Croup occurred for Omicron (n = 61, 5.3%) more than influenza virus (n = 601, 1.9%, adjusted RR = 2.0, 95%CI 1.5-2.6, p < 0.001) but not parainfluenza virus (n = 889, 5.4%). Our findings showed that for hospitalized children who had no past COVID-19 or vaccination, Omicron BA.2 was not mild. Omicron BA.2 appeared to be more neuropathogenic than influenza and parainfluenza viruses. It targeted the upper airways more than influenza virus.

Slower Recovery with Early Lopinavir/Ritonavir use in Pediatric COVID-19 Patients: A Retrospective Observational Study.

OBJECTIVES: There was initially insufficient understanding regarding suitable pharmacological treatment for pediatric Coronavirus Disease 2019 (COVID-19) patients. Lopinavir-ritonavir (LPV/r) was originally used for the treatment of Human Immunodeficiency Virus-1 (HIV-1) infection. It was also used in patients with severe acute respiratory syndrome (SARS) and Middle East Respiratory Syndrome (MERS) with positive results. Nonetheless, results from recent randomized controlled trials and observational studies on COVID-19 patients were unfavorable. We sought to evaluate the clinical outcomes associated with early treatment with LPV/r for pediatric COVID-19 patients. STUDY DESIGN: A total of 933 COVID-19 patients aged ≤ 18 years were admitted between 21 January 2020 and 31 January 2021 in Hong Kong. Exposure was receiving LPV/r within the first two days of admission. Time to clinical improvement, hospital discharge, seroconversion and hyperinflammatory syndrome, cumulative costs, and hospital length of stay were assessed. Multivariable Cox proportional hazard and linear models were performed to estimate hazard ratios (HR) and their 95% confidence intervals (CI) of time-to-event and continuous outcomes, respectively. RESULTS: LPV/r users were associated with longer time to clinical improvement (HR 0.51, 95% CI 0.38-0.70; p < 0.001), hospital discharge (HR 0.51, 95% CI 0.38-0.70; p < 0.001) and seroconversion (HR 0.59, 95% CI 0.43-0.80; p < 0.001) when compared with controls. LPV/r users were also associated with prolonged hospital length of stay (6.99 days, 95% CI 6.23-7.76; p < 0.001) and higher costs at 30 days (US$11,709 vs US$8270; p < 0.001) as opposed to controls. CONCLUSION: Early treatment with LPV/r for pediatric COVID-19 patients was associated with longer time to clinical improvement. Our study advocates the recommendation against LPV/r use for pediatric patients across age groups.

SARS-CoV-2 accessory proteins reveal distinct serological signatures in children.

The antibody response magnitude and kinetics may impact clinical severity, serological diagnosis and long-term protection of COVID-19, which may play a role in why children experience lower morbidity. We therefore tested samples from 122 children in Hong Kong with symptomatic (n = 78) and asymptomatic (n = 44) SARS-CoV-2 infections up to 200 days post infection, relative to 71 infected adults (symptomatic n = 61, and asymptomatic n = 10), and negative controls (n = 48). We assessed serum IgG antibodies to a 14-wide antigen panel of structural and accessory proteins by Luciferase Immuno-Precipitation System (LIPS) assay and circulating cytokines. Infected children have lower levels of Spike, Membrane, ORF3a, ORF7a, ORF7b antibodies, comparable ORF8 and elevated E-specific antibodies than adults. Combination of two unique antibody targets, ORF3d and ORF8, can accurately discriminate SARS-CoV-2 infection in children. Principal component analysis reveals distinct pediatric serological signatures, and the highest contribution to variance from adults are antibody responses to non-structural proteins ORF3d, NSP1, ORF3a and ORF8. From a diverse panel of cytokines that can modulate immune priming and relative inflammation, IL-8, MCP-1 and IL-6 correlate with the magnitude of pediatric antibody specificity and severity. Antibodies to SARS-CoV-2 internal proteins may become an important sero surveillance tool of infection with the roll-out of vaccines in the pediatric population.

Myopia incidence and lifestyle changes among school children during the COVID-19 pandemic: a population-based prospective study.

BACKGROUND: The impacts of social restrictions for COVID-19 on children's vision and lifestyle remain unknown. AIMS: To investigate myopia incidence, spherical equivalent refraction (SER) and lifestyle changes among schoolchildren during the COVID-19 pandemic. METHODS: Two separate longitudinal cohorts of children aged 6-8 years in Hong Kong were included. The COVID-19 cohort was recruited at the beginning of the COVID-19 outbreak, whereas the pre-COVID-19 cohort was recruited before the COVID-19 pandemic. All children received ocular examinations, and answered a standardised questionnaire relating to their lifestyle, including time spent on outdoor activities and near work, both at baseline and at follow-up visits. RESULTS: A total of 1793 subjects were recruited, of whom 709 children comprised the COVID-19 cohort with 7.89±2.30 months of follow-up, and 1084 children comprised the pre-COVID-19 cohort with 37.54±3.12 months of follow-up. The overall incidence was 19.44% in the COVID-19 cohort, and 36.57% in pre-COVID-19 cohort. During the COVID-19 pandemic, the change in SER and axial length was -0.50±0.51 D and 0.29±0.35 mm, respectively; the time spent on outdoor activities decreased from 1.27±1.12 to 0.41±0.90 hours/day (p<0.001), while screen time increased from 2.45±2.32 to 6.89±4.42 hours/day (p<0.001). CONCLUSIONS: We showed a potential increase in myopia incidence, significant decrease in outdoor time and increase in screen time among schoolchildren in Hong Kong during the COVID-19 pandemic. Our results serve to warn eye care professionals, and also policy makers, educators and parents, that collective efforts are needed to prevent childhood myopia-a potential public health crisis as a result of COVID-19.

Impact of COVID-19 Pandemic on School-Aged Children's Physical Activity, Screen Time, and Sleep in Hong Kong: A Cross-Sectional Repeated Measures Study.

Despite concerns about the negative effects of social distancing and prolonged school closures on children's lifestyle and physical activity (PA) during the COVID-19 pandemic, robust evidence is lacking on the impact of the pandemic-related school closures and social distancing on children's wellbeing and daily life. This study aimed to examine changes in the PA levels, sleep patterns, and screen time of school-aged children during the different phases of the COVID-19 outbreak in Hong Kong using a repeated cross-sectional design. School students (grades 1 to 12) were asked to report their daily electronic device usage and to fill in a sleep diary, recording their daily sleep onset and wake-up time. They were equipped with a PA monitor, Actigraph wGT3X-BT, to obtain objective data on their PA levels and sleep patterns. Students were recruited before the pandemic (September 2019-January 2020; n = 577), during school closures (March 2020-April 2020; n = 146), and after schools partially reopened (October 2020-July 2021; n = 227). Our results indicated lower PA levels, longer sleep duration, and longer screen time among participants recruited during school closures than those recruited before the COVID-19 outbreak. Primary school students were found to sleep on average for an extra hour during school closures. The later sleep onset and increased screen time documented during school closures persisted when schools partially reopened. Our findings illustrate the significant impact of social distancing policies during the COVID-19 pandemic on the sleep pattern, screen time, and PA level in school-aged children in Hong Kong. Professionals should urgently reinforce the importance of improving physically activity, good sleep hygiene, and regulated use of electronic devices for parents and school-aged children during this unprecedented time.

Influenza vaccine effectiveness against influenza-associated hospitalization in children in Hong Kong, 2010-2020.

BACKGROUND: Influenza virus infections can cause hospitalizations in children, and annual vaccination of children can provide protection against influenza. METHODS: We analyzed a test-negative design study with data spanning from 2010/11 through 2019/20 to evaluate influenza vaccine effectiveness (VE) against influenza hospitalization in children by age group, influenza type/subtype and time period within each season. We enrolled children admitted to hospital with acute febrile respiratory illnesses. Nasopharyngeal aspirates were tested by culture and/or RT-PCR to determine influenza status, and vaccination status was obtained by interviewing parents or legal guardians and was verified where possible. VE was estimated by conditional logistic regression model adjusting for sex, age and age-squared, matching on week. RESULTS: Influenza seasons in Hong Kong are prolonged with influenza-associated hospitalizations occurring in almost every month of the year during the study period. Influenza vaccination was effective in preventing influenza-associated hospitalizations in children of all ages. Influenza VE was higher in younger children than in older children, and higher against hospitalization due to influenza A(H1N1)pdm09 than A(H3N2) and B. CONCLUSIONS: The childhood influenza vaccination program in Hong Kong has prevented influenza-associated hospitalizations particularly in younger children. Our findings support the use of influenza vaccines in children as an effective approach to influenza control and prevention.