All day and sometimes into the night, buses and vans pull up to three state-funded medical screening centers near California's southern border with Mexico. Federal immigration officers unload migrants predominantly from Brazil, Cuba, Colombia, and Peru, most of whom await asylum hearings in the United States.

Once inside, coordinators say, migrants are given face masks to guard against the spread of infectious diseases, along with water and food. Medical providers test them for the coronavirus, offer them vaccines, and isolate those who test positive for the virus. Asylum-seekers are treated for injuries they may have suffered during their journey and checked for chronic health issues, such as diabetes or high blood pressure.

But now, as the liberal-leaning state confronts a projected $22.5 billion deficit, Gov. Gavin Newsom said the state can no longer afford to contribute to the centers, which also receive federal and local grants. The Democratic governor in January proposed phasing out state aid for some medical services in the next few months, and eventually scaling back the migrant assistance program unless President Joe Biden and Congress step in with help.

California began contributing money for medical services through its migrant assistance program during the deadliest phase of the coronavirus pandemic two years ago. The state helps support three health resource centers — two in San Diego County and one in Imperial County — that conduct covid testing and vaccinations and other health screenings, serving more than 300,000 migrants since April 2021. The migrant assistance program also provides food, lodging, and travel to unite migrants with sponsors, family, or friends in the U.S. while awaiting their immigration hearings, and the state has been covering the humanitarian effort with an appropriation of more than $1 billion since 2019.

Though the White House declined to comment and no federal legislation has advanced, Newsom said he was optimistic that federal funding will come through, citing "some remarkably good conversations" with the Biden administration. The president recently announced that the United States would turn back Cubans, Haitians, and Nicaraguans who cross the border from Mexico illegally — a move intended to slow migration. The U.S. Supreme Court is also now considering whether to end a Trump-era policy known as Title 42 that the U.S. has used to expel asylum-seekers, ostensibly to prevent the spread of the coronavirus.

Already, one potential pot of federal money has been identified. The Federal Emergency Management Agency and the U.S. Department of Homeland Security issued a statement to KHN noting that local governments and nongovernmental providers will soon be able to tap into an additional $800 million in federal funds through a shelter and services grant program. FEMA did not answer KHN's questions about how much the agency spends serving migrants.

“We're continuing our operations and again calling on all levels of government to make sure that there is an investment," said Kate Clark, senior director of immigration services for Jewish Family Services of San Diego, one of two main migrant shelter operators. The other is run by Catholic Charities for the Diocese of San Diego.

While health workers and immigration advocates want the state to continue funding, Newsom appears to have bipartisan support within the state for scaling it back. He promised more details in his revised budget in May, before legislative budget negotiations begin in earnest. And, he noted, conditions have changed such that testing and vaccination services are less urgent.

San Diego County Supervisor Nathan Fletcher, a Democrat, agreed that the burden should be on the federal government, though local officials are contemplating additional assistance. And state Senate Republican leader Brian Jones of San Diego, who represents part of the affected region, said that California is set to end its pandemic state of emergency on Feb. 28, months before the budget takes effect in July.

"The pandemic conditions no longer warrant this large investment from the state, especially since immigration is supposed to be a federal issue," Jones said in a statement.

California began its migrant assistance support soon after Newsom took office in 2019 and after the Trump administration ended the "safe release" program that helped transport immigrants seeking asylum to be with their family members in the United States. It was part of California's broad pushback against Trump's immigration policies; state lawmakers also made it a so-called sanctuary state, an attempt to make it safe from immigration crackdowns.

California, along with local governments and nonprofit organizations, stepped in to fill the void and take pressure off border areas by quickly moving migrants elsewhere in the United States. The state's involvement ramped up in 2021 as the pandemic surged and the Biden administration tried to unwind the Trump administration's "remain in Mexico" policy. While some cities in other parts of the country provided aid, state officials said no other state was providing California's level of support.

In a coordinated effort, migrants are dropped off at the centers by federal immigration officers, then are screened and cared for by state-contracted organizations that provide medical aid, travel assistance, food, and temporary housing while they await their immigration hearings.

Both Catholic Charities for the Diocese of San Diego and Jewish Family Service of San Diego coordinate medical support with the University of California San Diego. The federal government covers most of the university's costs while the state pays for nurses and other medical contractors to supplement health care, according to Catholic Charities.

It often takes one to three days before migrants can be put on buses or commercial flights, and in the meantime, they are housed in hotels and provided with food, clothing, and other necessities as part of the state's program.

“Many of them come hungry, starving," said Vino Pajanor, chief executive of Catholic Charities for the Diocese of San Diego, who described the screening and testing process at the centers. "Most of them don’t have shoes. They get shoes.”

Officials said about 46,000 people have been vaccinated against the coronavirus through the program. They said the figure is significantly lower than the number of migrants who have come through the centers because some were vaccinated before reaching the U.S. and younger migrants were initially ineligible, while others refused the shots.

According to the California Health and Human Services Agency, the state plans to phase out some medical support, but the sheltering operations are expected to continue "for the near term" with their future determined by the availability of federal funding. Of the more than $1 billion spent by the state, $828 million has been allocated through the Department of Public Health, according to the governor's office.

The agency said that while the state has not adopted specific plans to cut the sites' capacity, it will put a priority on helping families with young children and "medically fragile individuals" if the shelters are overwhelmed by arrivals.

Some immigration advocates said the state was making the wrong choice.

“Now’s the time for the state of California to double down on supporting those individuals that are seeking relief from immigration detention,” said Pedro Rios, who directs the U.S.-Mexico border program at the American Friends Service Committee, which advocates on behalf of immigrants. “I think it sends an erroneous message that the issues are no longer of concern."

This story was produced by KHN, which publishes California Healthline, an editorially independent service of the California Health Care Foundation.

This article was reprinted from khn.org with permission from the Henry J. Kaiser Family Foundation. Kaiser Health News, an editorially independent news service, is a program of the Kaiser Family Foundation, a nonpartisan health care policy research organization unaffiliated with Kaiser Permanente.