EL PASO — As influenza spread through migrant detention facilities last winter, the Centers for Disease Control and Prevention recommended that U.S. Customs and Border Protection vaccinate detained migrants against the virus, a push that CBP rejected, according to a newly released letter to Congress.

The CDC recommendation was revealed in a letter from the agency to Rep. Rosa L. DeLauro (D-Conn.), chair of the House Appropriations subcommittee that oversees funding for the Department of Health and Human Services, which includes the CDC. The agency’s director, Robert Redfield, issued the letter Nov. 7 in response to questions DeLauro posed last month after the flu had taken a toll on migrants in U.S. custody during the past year.

An 8-year-old Guatemalan boy died of the flu while being detained near El Paso in December, a month before the CDC’s vaccination recommendation. In the months after CBP rejected the recommendation, at least two children — one in El Paso and one in Weslaco, Tex. — died after being diagnosed with the flu in Border Patrol custody, autopsy reports showed. Influenza outbreaks in Border Patrol detention facilities continued through May, sickening hundreds of people, including agents and detainees.

DeLauro said CBP’s continuing refusal to provide flu vaccines to detained migrants is “unconscionable,” especially given Trump administration policies and migrant influxes that at times have caused U.S. facilities to be significantly overcrowded.

“CDC’s recommendations are clear: flu vaccines should be administered to people as soon as possible to prevent the spread of this deadly disease,” she said. “Worse still, administration policies that kept families locked in cages for extended periods of time greatly increased their risk of illness.”

Officials with CBP have never provided immunizations for detained migrants and does not plan to do so now, according to Kelly Cahalan, an agency spokeswoman.

“CBP has significantly expanded medical support efforts, and now has more than 250 medical personnel engaged along the Southwest border. To try and layer a comprehensive vaccinations system on to that would be logistically very challenging for a number of reasons,” she said. “The system and process for implementing vaccines — for supply chains, for quality control, for documentation, for informed consent, for adverse reactions — is complex, and those programs are already in place at other steps in the immigration process as appropriate.”

The two agencies that hold migrants for extended periods, Immigration and Customs Enforcement and the Office of Refugee Resettlement, provide flu vaccines. Adults and families who cross the U.S. border increasingly are being sent back to Mexico under the Migrant Protection Protocols program before they are turned over to ICE and thus do not get vaccinated. Unaccompanied children generally go to ORR shelters.

The CDC recommends that most people in the United States age 6 months and older receive a flu vaccination, as it is the primary preventive measure against what can be a potentially severe illness. In the 2018-2019 flu season, nearly 63 percent of children under the age of 18 received the flu vaccine and just more than 45 percent of adults received the vaccine.

CDC officials visited Border Patrol detention facilities in El Paso and Yuma, Ariz., in December and January, at CBP’s request. The CDC’s January report warned that because of inadequate medical infrastructure in the facilities, “illness in the Border Patrol facilities stresses both the Border Patrol staff and community medical infrastructure.”

The report made nine recommendations for minimizing the spread of the flu, and CBP adopted many of them, including expanding medical staff at detention facilities and increasing flu surveillance.

But CBP did not implement a recommendation for an aggressive vaccination program that would prioritize children and pregnant women.

In his Nov. 7 letter to DeLauro, Redfield reiterated the vaccination recommendation: “CDC recommends that priority should be given to the screening and isolation of ill migrants, early antiviral treatment, and flu vaccinations for all staff. CDC further recommends influenza vaccination at the earliest feasible point of entry for all persons at least six months of age, which is in concurrence with our general influenza vaccine recommendations.”

Other health experts also have recommended vaccines for migrants detained by CBP, especially children. A group of physicians that reviewed autopsy reports of children who died in CBP custody made that recommendation in an August letter to DeLauro and others in Congress.

A new report from the Brookings Institution warns that risk factors such as lackluster sanitation, overcrowding and poor nutrition are creating a “perfect storm” of conditions in CBP detention facilities that could lead to severe outbreaks of the flu and other communicable diseases. The report recommends vaccinating detained migrants as a way of limiting outbreaks.

Moore is a freelance journalist based in El Paso.