Physicians are urging US border officials to give flu vaccines to all migrant children held in detainment, local media reports.

Since September 2018, at least seven children have died in CBP custody, including three from complications from the flu. Prior to that, the immigration agency hadn’t reported any deaths in a decade.

“We believe that these outbreaks and deaths point to the urgent need for mandatory influenza immunization for children and an opt-out vaccination policy for adults in CBP detention centers, as well as required influenza immunization for employees at these centers,” said Dr. Carlo Foppiano Palacios, Dr. John Openshaw and Dr. Mark Travassos in the New England Journal of Medicine.