COVID-19 – understanding why children respond differently to infection compared to adults

During the COVID-19 pandemic, it quickly became apparent that children are generally less affected by the virus than adults. Dr Marko Nikolić of University College London has teamed up with Dr Kerstin Meyer at the Wellcome Sanger Institute to analyse individual cells from the nose lining or immune system of children and adults, to uncover clues that could help explain this phenomenon. The results could provide immediate benefits to help inform how to effectively treat or prevent severe illness in children and adults. In the longer term, improving the understanding of how the virus enters the body could help direct public health measures so the world can be better prepared for future pandemics.

How are children’s lives affected now?

Thankfully, most children infected with SARS-CoV-2 (the virus that causes COVID-19) will have mild symptoms or no symptoms at all. But while it is very rare, some children will develop severe disease.

“One of the biggest puzzles of the pandemic is why children are generally less affected by this virus than adults,” says Dr Nikolić. “We also don’t understand why some children are more susceptible to the disease than others.”

The virus enters the body by attaching to a specific molecule, which the research team has already shown is abundant on the surface of cells lining the nose in adults. Children may have lower amounts of this molecule, making it harder for it to infect their cells compared to older people. Their immune system may also react differently to the virus.

“Understanding why children are generally less affected by COVID-19 than adults could lead to new treatments and preventive measures that could help save lives from this disease around the world,” says Dr Nikolić.

How could this research help?

“We aim to identify biological differences that can help explain why age is a risk factor for severe disease – and why some children develop a life-threatening illness,” says Dr Nikolić.

The researchers have already collected nose and blood samples from healthy children – and they now also plan to recruit children with severe COVID-19.

“We will compare the molecular signatures of individual cells from adults and children, and between those with mild and severe disease, to gain new insights into how SARS-CoV-2 gains entry into the cell and how the immune system responds to the infection,” says Dr Nikolić.

The team will also apply sophisticated computer programmes to unpick how the immune system is triggered by the virus – and to look for any immune characteristics specific to children with mild symptoms.