NEW YORK (NYTIMES) - Just as millions of families around the United States navigate sending their children back to school at an uncertain moment in the pandemic, the number of children admitted to the hospital with Covid-19 has risen to the highest levels reported to date. Nearly 30,000 of them entered hospitals in August.

Paediatric hospitalisations, driven by a record rise in Covid-19 infections among children, have swelled across the country, overwhelming children's hospitals and intensive care units (ICUs) in states like Louisiana and Texas.

Children remain markedly less likely than adults, especially older adults, to be hospitalised or die from Covid-19.

But the growing number of children entering the hospital, however small compared with adults, should not be an afterthought, experts say, and should instead encourage communities to increase their efforts to protect their youngest residents.

"It should concern us all that hospitalisations - indicators of severe illness - are rising in the paediatric population, when there are a lot of steps we could take to prevent many of these hospitalisations," said Mr Jason Salemi, a public health researcher at the University of South Florida, who tracks Covid-19 hospitalisation data.

Public health officials and experts also caution that even small increases in the number of paediatric Covid-19 patients can put a major strain on paediatric hospitals and ICUs, many of which are already overstretched with nursing shortages and an unusual summer surge of respiratory syncytial virus, or RSV.

"The average paediatric ICU in the US has 12 beds," said Dr Christopher Carroll, a paediatric intensivist at Connecticut Children's Medical Centre. "In a system that small, even a few patients can quickly overrun the capacity. And there are fewer speciality trained paediatric clinicians to pick up the slack."

The strain on hospital resources for children has prompted doctors and hospital executives to plead with adults to get vaccinated and return to mask wearing and social distancing to protect children, especially those younger than 12, who cannot yet be vaccinated.

"What really protects children are the interventions directed at the rest of society," said Dr Thomas Tsai, an assistant professor in the health policy department at Harvard University.

State-level vaccination coverage appears to be making a difference. States with the highest vaccination rates in the country have seen relatively flat paediatric hospital admissions for Covid-19 so far, while states with the lowest vaccine coverage have child hospital admissions that are around four times as high.

During the summer surge, the hospitalisation rate was about 10 times as high in unvaccinated adolescents as in those who were vaccinated, according to a recent federal study.

But data on hospitalisations among children of different ages is limited. A federal survey offers a breakdown for infants, children and adolescents, but it is based on 14 states, many of which have not experienced the worst of the wave led by the Delta variant of the coronavirus.

Scientists have said that there is not yet enough evidence to determine whether the Delta strain causes more severe disease in children than other variants.

There is no doubt, on the other hand, that paediatric hospitalisations have been pushed to new highs because Delta's greater transmissibility has led to record levels of adult and paediatric cases of Covid-19 across the country.

More child Covid-19 cases - greater than 250,000 - were recorded in the past week than at any previous point in the pandemic, according to the most recent American Academy of Paediatrics survey of state data. More than five million children have tested positive for Covid-19 since the pandemic's start.

Public health experts caution that the magnitude of childhood infections matters even if most cases are mild, because scientists are still working to understand the long-term effects of the disease, including "long Covid", the presence of lingering neurological, physical or psychiatric symptoms after Covid-19 infection.

"These are children whose development and futures may be compromised," said Dr James Versalovic, interim paediatrician-in-chief at Texas Children's Hospital. "The collective impact when we look ahead is significant."

He added: "Children are our future adults."