The number of US children killed by guns soared by 50% between 2019 and 2021 as the country grappled with COVID-19 — a grim increase that was felt hardest among black youth in cities governed by Democrats.

Only a small fraction of the soaring gun violence involved school shootings, and black children were five times more likely than their white counterparts to die at the hands of a shooter, according to a new Pew Research Center report.

Overall, fatal gun violence rose across the country and among all age groups during the pandemic, with a 23% increase in shooting deaths among Americans recorded during the three years.

There were 48,830 gun deaths specifically recorded in 2021 — the most in a single year since 1999, when the federal Centers for Disease Control and Prevention first began keeping such stats, the report said.

Although children under 18 made up a small fraction of the overall rise in gun fatalities for the three-year period, their age group suffered the worst rate of increase.

In the year before the pandemic hit, 1,732 children in America died from guns. Two years later, that figure was up to 2,590, the report said.

Boys accounted for 83% of the firearm fatalities in 2021, and 46% of the total young victims were black, even though black children constituted of only 14% of the US minor population at the time, the study said.

Sixty percent of the young lives lost in 2021 involved homicides, and 32% were suicides, with the remaining deaths falling under the categories of accidents or “other,” researchers said.

But the causes of death were starkly different among racial lines: The vast majority of gun deaths among black teens and children, or 84%, were caused by homicides, while most gun deaths among white children, 66%, were ruled suicides, researchers found.

The gun-death rate among Hispanic youth was the same as among white children

Meanwhile, school shootings accounted for fewer than 2% of the total related death toll in 2021, when 49 people were killed in 202 gun incidents at US schools, according to Everytown Research & Policy, an independent gun safety organization.

In New York City, 21 kids were fatally shot in 2021, a significant increase from 11 young victims reported in 2020 and five the year before that, according to the NYPD.

But children were safer from gun violence in the Big Apple than the nation as a whole for the three years: Almost 3% of the US population lives in the five boroughs, but fewer than 1% of the country’s youth shooting deaths happened there, an evaluation of the statistics showed.

The toll of deadly youth gun violence was far higher in comparable US cities in 2021. In Philadelphia, 36 minors were killed by guns, a grim new murder record for the City of Brotherly Love, according to WCAU-TV. In Chicago, at least 106 people under the age of 20 also died at the hands of a shooter, the Chicago Tribune reported on New Year’s Eve that year.

The newspaper noted that the majority of the young victims were black males and that the violence was concentrated in Windy City neighborhoods that are effectively racially segregated.

As violence raged in Democrat-controlled urban areas, a poll conducted by Pew Research Center found that Dem-leaning voters were almost twice as concerned about their children getting shot than their Republican counterparts.

Twenty-seven percent of Democrats polled by the group said they were “extremely” or “very” concerned about the bleak trend, while only 14% of Republicans felt the same way.

Only 10% of high-income parents shared a grave level of concern about the issue, compared to 40% of low-income respondents. Hispanic and black parents were also much more likely to be “extremely” concerned about youth gun violence than white parents, and worries were much more heightened in urban areas than in rural and suburban ones.

The Pew Research Center did not respond to an interview request from The Post on Monday.