Stephen Miller is on a roll

The U.S. won’t be vaccinating migrant families in holding centers ahead of this year’s flu season, despite calls from doctors to boost efforts to fight the infection that’s killed at least three children at detention facilities in the past year.

“In general, due to the short-term nature of CBP holding and the complexities of operating vaccination programs, neither CBP nor its medical contractors administer vaccinations to those in our custody,” a Customs and Border Protection spokeswoman said in an emailed statement.

At least three children who were held in detention centers after crossing into the U.S. from Mexico have died in recent months, in part, from the flu, according to a letter to Reps. Rosa DeLauro, D-Conn., and Lucille Roybal-Allard, D-Calif., from several doctors urging Congress to investigate health conditions at the centers.

The United States had previously gone almost a decade without any children dying while under U.S. immigration custody.

The Trump administration unveiled a regulation on Wednesday that would allow it to detain indefinitely migrant families who cross the border illegally, replacing a decades-old court agreement that imposed a limit on how long the government could hold migrant children in custody and specified the level of care they must receive.

The White House has for more than a year pressed the Department of Homeland Security to replace the agreement, known as the Flores settlement, a shift that the administration says is crucial to halt immigration across the southwestern border.

The new regulation, which requires approval from a federal judge before it could go into effect and was expected to be immediately challenged in court, would establish standards for conditions in detention centers and specifically abolish a 20-day limit on detaining families in immigration jails, a cap that has prompted President Trump to repeatedly complain about the “catch and release” of families from Central America and elsewhere into the United States.

“This rule allows the federal government to enforce immigration laws as passed by Congress,” Kevin K. McAleenan, the acting secretary of homeland security, said in a statement. He called it a “critical rule” that would allow the government to detain families and maintain the “integrity of the immigration system.”

The administration proposed the rule last fall, allowing the public to comment on the potential regulation. It is scheduled to be published this week in the Federal Register and would take effect 60 days later, though administration officials concede that the expected court challenge will probably delay it.

[The Flores agreement protected migrant children for decades.]

Under the new rule, the administration would be free to send families who are caught crossing the border illegally to a family residential center to be held for as long as it takes for their immigration cases to be decided. Officials said families cases could be resolved within three months, though many could drag on much longer.

Trump administration officials — who briefed reporters on Tuesday night on the condition of anonymity to discuss the plans — said that many of the families would be detained until they were either released after being awarded asylum or they were deported to their home countries. Some families might be awarded parole to leave the facilities while the courts decide their fate.

The 20-day limit has been in place since 2015, a legal outgrowth of a 1997 court-ordered consent decree after a federal class-action lawsuit alleged physical and emotional harm done to immigrant children held for extended periods of time in the detention facilities.

Previous administrations tried to change the rules for detaining children in efforts to reduce surges of migrants crossing the border. Mr. Trump’s homeland security officials have repeatedly said that limiting the detentions of entire migrant families has driven the surge of Central American families who crossed the border this year.

The officials said on Tuesday that enacting the new regulation would send a powerful message that bringing children to the United States was not “a passport” to being released from detention.

They predicted that the rule would cause a significant decrease in the number of families trying to cross into the United States illegally, reducing the need for more family residential centers.

Withdrawing from the consent decree has also been a personal objective for Stephen Miller, the architect of Mr. Trump’s immigration policy. Delays in finishing the new regulation had prompted Mr. Miller to lash out at senior homeland security officials, who were ousted from the department.

The New York Times reported in April that Mr. Miller berated the former acting director of Immigration and Customs Enforcement, Ronald D. Vitiello, for not finishing the new rule. Mr. Vitiello later had his nomination withdrawn by Mr. Trump, who said he was not tough enough for the job.