Almost 13 million children in the United States have tested positive for COVID-19 since the onset of the pandemic, according to the latest report by the American Academy of Pediatrics (AAP) and the Children's Hospital Association.

Over 149,000 of these cases were added in the past four weeks. Over 5 million reported cases were added in 2022, according to the report published late Monday.

Children represented 19 per cent of all COVID-19 cases in the country, the report showed.

Over 53,000 child COVID-19 cases were reported in the week ending April 28, an increase of over 60 per cent from two weeks ago.

This marked the third consecutive weekly increase in reported child cases, according to the AAP.

There is an urgent need to collect more age-specific data to assess the severity of illness related to new variants as well as potential longer-term effects, said the AAP.

"It is important to recognize there are immediate effects of the pandemic on children's health, but importantly we need to identify and address the long-lasting impacts on the physical, mental, and social well-being of this generation of children and youth," said the AAP.