Health experts are concerned about the sharp rise in COVID-19 cases in children just as Pfizer submitted its initial trial data for its vaccine.

Long Island currently has the second highest number of COVID-19 cases among students in the state, according to the state's COVID-19 Report Card system. 

Close to 4,000 lab-verified cases were found among children 5 to 17 years old on Long Island, according to state officials. 

That number is second only to New York City, which reportedly showed just over 6,200 cases.

Dr. Matthew Harris, the medical director of Northwell Health Vaccination Program, appeared on News 12's the New Normal Tuesday morning to discuss COVID cases in children. 

“We know that hospitalization rates in general for kids remain low, but have increased substantially, and a quarter— 26% of all children who are hospitalized - are hospitalized in the intensive care unit,” he said.

These numbers came on the same day that Pfizer submitted initial trial data for its COVID-19 vaccine in children ages 5 to 11. 

Harris points out that the vaccine dose will be just one-third of what is given to adults.

He also says that most of the children who have been hospitalized for the virus “are unvaccinated either by age or by choice— those younger adolescents that are 12 and older. This remains a huge concern.”

The heads of the both the Nassau and Suffolk Schools Superintendents Association released a joint statement that said in part, “While the rise in COVID-19 cases in our region and in our schools is concerning, school districts throughout Long Island remain vigilant in enforcing our health and safety protocols... and we ask for our communities' continued collaboration in adhering to this guidance.”

Peter Silver, the medical director at Cohen Children's Medical Center, says, “My message to parents is that once their children are eligible for vaccinations: please get them vaccinated. It's something we need to do to eliminate this virus."

Silver adds that while Long Island is not out of the woods yet when it comes to COVID, it is headed in the right direction.

“Last week, we admitted four children with COVID and released another 16 from our emergency department,” he says.

Pfizer officials say they will make a formal request with U.S. regulators for emergency use of the vaccine for children in the weeks to come.