Households, not schools, major SARS-CoV-2 transmission route among HK children

Natalia Reoutova
12 Oct 2021
Households, not schools, major SARS-CoV-2 transmission route among HK children
Back row (from left): Dr Wilfred Wong, Professor Ian Wong, Dr Winnie Tso, Prof Wing-Hang Leung. Front row (from left): Dr Kelvin To, Dr Patrick Ip, Dr Mike Kwan

Households, and not schools, are the major route of coronavirus disease 2019 (COVID-19) transmission for those 18 years of age, according to a cross-sectional study of nearly 400 Hong Kong children and youths who contracted COVID-19 in 2020.

“While US studies found that severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] infection in children and youths was not associated with attending schools or childcare centres, and secondary transmission within schools was rare, evidence concerning COVID-19 outbreaks in Hong Kong schools was lacking,” wrote the researchers from the University of Hong Kong (HKU). [MMWR Morb Mortal Wkly Rep 2020;69:1925-1929; Pediatrics 2021;doi:10.1542/peds.2020-048090] “Therefore, we conducted this study to identify the sources of infection among children and youths with COVID-19 during the first three waves of outbreaks in Hong Kong.”

The study included 397 children and youths with COVID-19 (male, 55 percent; mean age, 10 years) captured in the central database between January and December 2020. Across the three waves, 204 patients (51.4 percent) had domestic infections. [JAMA Netw Open 2021;doi:10.1001/jamanetworkopen.2021.8824]

Most patients (n=273; 68.8 percent) reported a contact history with another COVID-19 patient, with almost all of those contacts being infected family members (270 individuals; 98.9 percent) – mainly parents, grandparents, and siblings. In the first wave, three individuals with imported infections reported having contacts with other infected schoolmates at overseas boarding schools, as did six individuals in the second wave. In the third wave, only three individuals with domestic reported having contacts with infected schoolmates; these contacts occurred >1 month after the May 2020 school reopening.

“Our study found that SARS-CoV-2 transmission within school campuses in Hong Kong was rare, regardless of whether schools were closed or reopened. There were no reports that teachers had transmitted COVID-19 to their students,” wrote the researchers.

“Our results clearly showed that close contact with parents and grandparents was the primary route through which Hong Kong children and adolescents acquired COVID-19, indicating an urgent need for eligible adults to get vaccinated,” said co-corresponding author, Dr Patrick Ip of the Department of Paediatrics and Adolescent Medicine, HKU.

After the closure of schools, many students switched their learning to online platforms, with considerable physical and social implications. A study conducted by the Hong Kong Eye Hospital found significantly greater myopia progression in children during the home confinement period vs the pre–COVID-19 period. [Zhang XJ, unpublished data, 2021] Another prospective study in China, recently reported by MIMS Doctor, found a 1.4-  to 3-fold increase in myopia prevalence in 2020 vs the previous 5 years. [JAMA Ophthalmol 2021;doi:10.1001/jamaophthalmol.2020.6239]

Furthermore, a HKU research showsd that school closures in Hong Kong have had a significant adverse impact on children’s wellbeing, particularly in children with special education needs, families with members who had mental health problems, as well as single-parent and lower-income families. [Eur Child Adolesc Psychiatry 2020;doi:10.1007/s00787-020-01680-8]

“Children’s psychosocial wellbeing has evidently been affected by extended school closure; more caution and precision are desirable for any future closures,” said co-author, Dr Mike Kwan of Department of Paediatrics and Adolescent Medicine, HKU. “For children with special needs and other vulnerable groups, it is essential to maintain, or minimize disruption to, medical and rehabilitation care during the pandemic.”

“Eligible persons 16 years of age in the household or caregivers of children and youths should receive COVID-19 vaccination to protect themselves and younger generation, for whom no licensed vaccine is available,” he concluded.


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