COVID-19 vaccines versus pediatric hospitalization.

Vaccine effectiveness of BNT162b2 and CoronaVac against COVID-19-associated hospitalization and moderate-to-severe disease due to SARS-CoV-2 Omicron BA.2 is studied from the 1.36 million doses administered to 766,601 of 953,400 children aged 3-11 years and adolescents aged 12-18 years in Hong Kong as of April 2022. These vaccines confer substantial protection.

Effectiveness of BNT162b2 and CoronaVac in children and adolescents against SARS-CoV-2 infection during Omicron BA.2 wave in Hong Kong.

BACKGROUND: The SARS-CoV-2 Omicron BA.2 subvariant replaced BA.1 globally in early 2022, and caused an unprecedented tsunami of cases in Hong Kong, resulting in the collapse of elimination strategy. Vaccine effectiveness (VE) of BNT162b2 and CoronaVac against BA.2 is unclear. METHODS: We utilize an ecological design incorporating population-level vaccine coverage statistics and territory-wide case-level SARS-CoV-2 infection surveillance data, and investigate the VE against infection during the Omicron BA.2 wave between January 1 to April 19, 2022, in Hong Kong for children and adolescents. RESULTS: We estimate VE to be 33.0% for 1 dose of BNT162b2 in children aged 5-11 and 40.8% for 2 doses of CoronaVac in children aged 3-11. We also estimate 54.9% VE for 2 doses of BNT162b2, and 55.0% VE for 2 doses of CoronaVac in adolescents aged 12-18. CONCLUSIONS: Our findings support partly preserved VE against infection by variants of concerns for children and adolescents in settings with extremely low levels of prior SARS-CoV-2 circulation.

COVID-19 vaccines BNT162b2 and CoronaVac are widely used globally in children and adolescents, yet their effectiveness against Omicron BA.2 variant­a version of the SARS-CoV-2 virus that became predominant in early 2022­is not fully known. In Hong Kong, we combine population-level vaccine coverage statistics and territory-wide SARS-CoV-2 infection data, and estimate their effectiveness against SARS-CoV-2 infection in children and adolescents during a major Omicron BA.2 outbreak. We find moderate vaccine effectiveness after 2 doses of BNT162b2 or CoronaVac, supporting the use of either vaccine in children and adolescents during a rapidly evolving pandemic.

Age- and Sex-Specific Physical Fitness Reference and Association with Body Mass Index in Hong Kong Chinese Schoolchildren.

There is lacking a population-based study on the fitness level of Hong Kong schoolchildren, and it seems that increasing childhood obesity prevalence has shifted the classification of healthy fitness, with 'underfit' as normal. This cross-sectional territory study aimed to develop an age- and sex-specific physical fitness reference using a representative sample of children aged 6-17 and to determine the associations with body mass index in schoolchildren. The study analyzed Hong Kong School Physical Fitness Award Scheme data covering grade 1 to grade 12 students' physical fitness and anthropometric measurements from 2017 to 2018. This reference was established without the impact due to COVID-19. Four aspects of physical fitness tests were measured using a standardized protocol, including (i) upper limb muscle strength, (ii) one-minute sit-up, (iii) sit-and-reach, and (iv) endurance run tests. The generalized additive model for location, scale, and shape was used to construct the reference charts. A Mann-Whitney U test was used to compare the mean differences in age, weight, and height, and a Pearson's chi-square test was used to examine the distributions of sex groups. A Kruskal-Wallis test was used to compare the group differences in BMI status, followed by the Dunn test for pairwise comparisons. A 5% level of significance was regarded as statistically significant. Data of 119,693 students before the COVID-19 pandemic were included in the analysis. The association between physical fitness level and BMI status varied depending on the test used, and there were significant differences in fitness test scores among BMI groups. The mean test scores of the obese group were lower in most of the tests for both boys and girls, except for handgrip strength. The underweight group outperformed the obese group in push-ups, one-minute sit-ups, and endurance run tests, but not in handgrip strength. In conclusion, a sex- and age-specific physical fitness reference value for Hong Kong Chinese children aged 6 to 17 years old is established, and this study demonstrated a nonlinear relationship between BMI status and physical fitness. The reference will help to identify children with poor physical fitness to offer support and guidance on exercise training. It also serves as a baseline for assessing the impact of the COVID-19 pandemic on Hong Kong students' physical fitness.

Identifying the High-Risk Population for COVID-19 Transmission in Hong Kong Leveraging Explainable Machine Learning.

The worldwide spread of COVID-19 has caused significant damage to people's health and economics. Many works have leveraged machine learning models to facilitate the control and treatment of COVID-19. However, most of them focus on clinical medicine and few on understanding the spatial dynamics of the high-risk population for transmission of COVID-19 in real-world settings. This study aims to investigate the association between population features and COVID-19 transmission risk in Hong Kong, which can help guide the allocation of medical resources and the implementation of preventative measures to control the spread of the pandemic. First, we built machine learning models to predict the number of COVID-19 cases based on the population features of different tertiary planning units (TPUs). Then, we analyzed the distribution of cases and the prediction results to find specific characteristics of TPUs leading to large-scale outbreaks of COVID-19. We further evaluated the importance and influence of various population features on the prediction results using SHAP values to identify indicators for high-risk populations for COVID-19 transmission. The evaluation of COVID-19 cases and the TPU dataset in Hong Kong shows the effectiveness of the proposed methods. The top three most important indicators are identified as people in accommodation and food services, low income, and high population density.

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.

A mixed-methods study on the association of six-month predominant breastfeeding with socioecological factors and COVID-19 among experienced breastfeeding women in Hong Kong.

BACKGROUND: In the past decade, various breastfeeding policies were implemented in Hong Kong, including changes in perinatal guidelines in public hospitals, adoption of the Baby-Friendly Hospital Initiative (BFHI), provision of guidelines for the marketing of formula milk, penalisation of discrimination towards breastfeeding, and extension of the statutory maternity leave. Meanwhile, the COVID-19 pandemic brought new challenges and opportunities to breastfeeding practices. Infection control measures in public hospitals included the cancellation of antenatal classes, hospital tours, and postnatal classes; suspension of perinatal visiting periods; and compulsory separation of COVID-19 positive mothers from newborns. In addition, work-from-home policies were widely implemented. This study aimed to identify the associated factors of six-month predominant breastfeeding (PBF), and to evaluate the impact of COVID-19 on breastfeeding practice. METHODS: This study was conducted from 1 March 2021 to 7 April 2021 using a mixed-methods approach. An electronic questionnaire was distributed to members of breastfeeding or parenting groups who have had breastfeeding experience in the past 10 yrs. Logistic and linear regression analyses were conducted to identify factors associated with six-month PBF both in general and during the pandemic period. A qualitative content analysis was conducted using an inductive approach. RESULTS: The study included 793 participants. Giving birth in a public hospital (OR 2.21; 95% CI 1.46, 3.34) and breastfeeding support from family and friends (OR 1.28; 95% CI 1.05, 1.57) were significantly associated with six-month PBF, even during COVID-19. Factors associated with the self-rated impact of COVID-19 on breastfeeding include working from home, the perceived immunological benefits of breastfeeding, and the wish to avoid breastfeeding or expressing breast milk in public premises. Furthermore, breastfeeding practice in public hospitals was more likely to be affected by the busyness of staff, while private hospitals had worse rooming-in practices and staff who had inadequate breastfeeding knowledge. CONCLUSIONS: Giving birth in a public hospital and having breastfeeding support from family and friends were associated with six-month PBF. Furthermore, COVID-19 in Hong Kong had an overall positive impact on six-month PBF. Further studies should investigate the impact of hospital practices and the COVID-19 pandemic on breastfeeding behaviours.

Impact of a focus education in Zoom on COVID-19 vaccine hesitancy in Hong Kong parents of the preschoolers.

Parental vaccine hesitancy is a major barrier to achieving high vaccination uptake among children, particularly in young children during the coronavirus disease 2019 (COVID-19) pandemic. Developing herd immunity is a critical concept for overcoming the current pandemic. The purpose of this study is to reduce parental vaccine hesitancy through a focused educational seminar in ZOOM and to empower parents who are concerned about vaccinating their children to communicate with medical experts during live seminars. Parents of preschoolers, teachers, and kindergarten principals from three local pre-school education and services associations attended live seminars. After attending seminars, parental willingness to vaccinate their children increased by 65%. The live Zoom seminar led by medical experts resulted in a decrease in vaccine hesitancy. Our findings support the creation of seminars that allow clients and medical specialists to communicate directly with one another. Offering an open and honest forum for people to express their concerns to medical experts could be a useful strategy for dealing with not only vaccination apprehension, but also other health-related emergencies.

Survey data on the attitudes of adolescents in Hong Kong towards the COVID-19 vaccination.

To our best knowledge, this article presents a novel data set on Hong Kong's adolescents' attitude towards the COVID-19 vaccination, excluding their parental opinions. This research used a cross-sectional questionnaire survey, which collects data from the population at a single point in time. Our questionnaire was designed in both English and Chinese for the adolescents' convenience, using a self-designed, online questionnaire website, which was sent to 30 secondary schools across Hong Kong at the beginning of June 2021, to be completed by 31st June 2021. This gathered a total of 2609 surveys, excluding those which did not fit into the criteria. As the data has identified factors that affect vaccine hesitancy, government authorities can use the data to choose effective ways to promote the COVID-19 vaccination and to educate the general population about the benefits of receiving it.

Impact of COVID-19 Pandemic on Serum Vitamin D Level among Infants and Toddlers: An Interrupted Time Series Analysis and before-and-after Comparison.

Background: During the coronavirus disease 2019 (COVID-19) pandemic, the implementation of social distancing and home confinement measures may elevate the risk of vitamin D deficiency particularly for infants. This study aimed to quantify changes in vitamin D level among infants and toddlers in Hong Kong after the COVID-19 outbreak. Methods: We recruited 303 infants and toddlers aged 2-24 months by stratified random sampling from 1 June 2019 to November 30, 2020. Regression models were used to estimate the effect of time on infants' serum 25-hydroxyvitamin D (25(OH)D) level overall and by age groups before and after the outbreak. Interrupted time series (ITS) analysis was performed to examine the sustained effect of COVID-19 on their serum 25(OH)D level. Results: The ITS results showed no immediate reduction in serum 25(OH)D level among infants, but a decreasing trend was observed in the subsequent months post-outbreak at a monthly decline rate of -6.32 nmol/L. When analyzed by age group, the magnitude of post-outbreak reduction in 25(OH)D was stronger among younger infants (aged 2-6 months). Conclusion: Guidelines and recommendations should be given to pregnant women and mothers to ensure sufficient vitamin D level in their infants during the COVID-19 period.