Children under 5 at lowest risk of getting Covid-19 from adults: KKH study

The risk of secondary infection in children was highest if the first identified patient was the child's mother (11.1 per cent), as compared to the father (6.7 per cent) or grandparent (6.3 per cent).
PHOTO: Pexels

A household transmission study conducted by the KK Women’s and Children’s Hospital (KKH) found that children under five years old had the lowest risk of getting infected by adults as they may be more resistant to the virus.

From March to April 2020, researchers looked at 213 children under 16 years old who were tested for Covid-19. They would be tested if an adult in the same household was diagnosed with the disease.

Among the 137 households with confirmed Covid-19 exposure that were surveyed, 13 cases of adult-to-child transmission were detected across seven households, according to results published on Tuesday (Oct 13).

Children under five years of age were found to have lower rates of getting infected by adults as compared to older children, following exposure to a household member with Covid-19.

The adult-to-child transmission rate is as follows:

  • 1.3 per cent for children under five 
  • ​8.1 per cent for children aged ​five to nine
  • 9.8 per cent for children aged 10 to 16  

“The very low adult-to-child transmission rate among young children under five years old in households may suggest that strict compliance with infection control may be able to mitigate or reduce the risk of transmission from adults to children in household settings,” said Dr Yung Chee Fu, consultant at the KKH’s Infectious Disease Service.

PHOTO: Pexels

He adds that this trend may be due to the “increased expression of the angiotensin-converting enzyme 2 receptors (the receptor that Sars-CoV-2 uses for host entry) in the nasal epithelium with increasing age, thus it is possible that younger children are more resistant to Sars-CoV-2 infection at a cellular level”.

Researchers also found that the adult-to-child transmission rates were similar regardless of the child’s gender. 

Additionally, results showed that the risk of secondary infection in children was highest if the first identified patient was the child’s mother (11.1 per cent), as compared to the father (6.7per cent) or grandparent (6.3 per cent). 

“Understanding how Covid-19 affects children differently from adults is very important to guide clinical management of children with Covid-19 and recommendations for public health measures,” says Dr Yung.

Young children may not be primary drivers of Covid-19 transmission in schools

According to researchers, Covid-19 transmission among children in schools, especially preschool, is likely to be low.

This can be seen from the screening results of students from a secondary school and two preschools after a Covid-19 case was detected in the schools. The incidents were identified in February and March 2020. 

Close contacts of the two infected students — a 12-year-old secondary school student and a five-year-old from one of the two preschools — tested negative for the virus.

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Likewise, students at the other preschool were also not infected by Covid-19 despite an adult staff member being diagnosed with Covid-19. 15 other staff members were subsequently confirmed to have Covid-19.

“The clinical manifestation of Covid-19 in children has been reported to range from asymptomatic to moderate rather than severe, but the burden of disease and the paediatric role in community transmission has remained largely unknown,” shares Dr Yung Chee Fu.

“These findings suggest that the risk of SARS-CoV-2 transmission among children especially young children in pre-school settings, is likely to be low. More school transmission studies are urgently needed to inform the development of evidence based strategies to control Covid-19 in our educational settings.”

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This article was first published in theAsianparent.