More than six million children have tested positive for COVID-19 during the pandemic, according to data collected by the American Academy of Pediatrics (AAP) and the Children's Hospital Association.

As of October 7, over 6.04 million American children had contracted the virus, said the report. There was a 6 percent increase in the cumulated number of child COVID-19 cases in the two weeks from September 23 to October 7, as the school season began and vaccines for children under 12 were still waiting for approval.

Pfizer Inc. and German partner BioNTech SE said on Friday that they had submitted data supporting the use of their COVID-19 vaccine in children aged between five and 12 to the European Medicines Agency.

Although the vaccine is currently not allowed for that age group, it has been authorized for use in children over 12 years of age in both the United States and the European Union. The U.S. health regulator is delaying its decision on authorizing Moderna Inc.'s COVID-19 vaccine for adolescents to check if the shot could increase the risk of a rare inflammatory heart condition.

The number of new child COVID-19 cases remains exceptionally high, according to the AAP. Over 148,000 cases were added between September 30 and October 7, accounting for about a quarter of the weekly reported cases. Over 750,000 child cases were added over the past four weeks.

Children make up from 1.6 percent to 4.2 percent of COVID-19 cases in the U.S. and 0.1 percent to 2.0 percent of all child COVID-19 cases in the country result in hospitalization, according to the AAP.

Child COVID-19 cases have been climbing steadily since July, from about 38,000 cases on July 22 to 180,000 in mid-August, according to The Wall Street Journal.

(With input from agencies)