Firearms killed more people aged one to 19 in the States than car crashes, drug overdoses, or cancer, according to an analysis of government data published by researchers in April.
More than 4,300 died of firearm-related injuries that year, according to the analysis by University of Michigan researchers - a 29 percent increase from 2019.
The research letter, which was published in the New England Journal of Medicine, analysed decades of mortality data from the Centers for Disease Control and Prevention (CDC).
“In the last 40 years, and almost certainly before that, this is the first time that firearm injuries have surpassed motor vehicle crashes among kids,”Jason Goldstick, a research associate professor at the University of Michigan, told NBC News.
He said homicides, rather than suicides, made up the majority of those firearm deaths among children and teens in 2020.
“The increasing rates of firearm mortality are a longer-term trend and demonstrate that we continue to fail to protect our youngest population from a preventable cause of death," he said.
Car accidents remain the second leading cause of death in the group,with around 3,900 fatalities among children and teenagers.
Researchers said these had “drastically decreased” over the last two decades, likely because of car safety improvements.
The third leading cause of death was drug poisoning deaths, which included overdoses, which increased by more than 83% to more than 1,700 in the age group.
The research found: “Although the new data are consistent with other evidence that firearm violence has increased during the Covid-19 pandemic, the reasons for the increase are unclear, and it cannot be assumed that firearm-related mortality will later revert to pre-pandemic levels.”
It added that “funding momentum” must be maintained into the prevention of gun violence among youngsters.
The latest data comes after President Joe Biden vowed in April to crack down on so-called ghost guns and ban the manufacturing of the untraceable firearms as part of his gun crime prevention efforts.
Ghost guns are privately made firearms that are not marked with a serial number and are difficult for law enforcement to trace when used to commit a crime.