Los Angeles, March 1 : Almost 15.5 million children in the US are reported to 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 121,000 of these cases have been added in the past four weeks, and almost 28,000 child Covid-19 cases were reported in the latest week ending February 23, Xinhua news agency reported, citing the report. Over the past five months, weekly reported child cases in the United States have plateaued at an average of about 32,000 cases. Reported cases are likely a "substantial undercount" of Covid-19 cases among children, according to the report. There is a 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 report. 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. /IANS