Earlier this month, after learning that three children had recently died from the flu while in the custody of the U.S. Customs and Border Protection (CBP), a group of doctors decided to act.

The doctors belong to a group called Doctors for Camp Closure, which describes itself as “physicians coming together to fight the human rights violations against asylum seekers and immigrants coming to the U.S.” Among them is Julie Sierra, M.D., an internal medicine doctor in San Diego.

“The problem is that [CBP] is keeping people in conditions that greatly increase their risk of getting sick with the limited hygiene,” she told VICE.

Together, the doctors sent a letter to the Department of Homeland Security, which oversees CBP, offering to provide and administer free flu vaccines to migrants in detention in California. The letter, sent on November 5, gave the DHS and CBP a two-week deadline for response. On Tuesday, that deadline came and went without a reply.

The three children who died in CBP custody of flu complications were ages 2, 6, and 16. The doctors’ letter pointed out that the children’s deaths indicate a flu death rate inside CBP facilities that is nine times higher than the general pediatric population. Overall, a minimum of seven children have died in CBP facilities since last year, an enormous uptick when compared to previous years, when no deaths of children in border patrol custody were reported.

CBP says that it does not provide medical care, like flu vaccines, to migrants in custody because they are only supposed to hold people for a short period of time: no more than 72 hours. “It has never been a CBP practice to administer vaccines and this not [sic] a new policy,” a CBP spokesperson told VICE. But numerous reports have shown that migrants, including children, are often held by CBP for much longer than three days. One DHS report found that nearly a third of children and about 43 percent of all detainees in CBP custody were held for longer than that.

“While Individuals in CBP custody should generally not be held for longer than 72 hours in either CBP hold rooms or holding facilities, every effort is made to hold detainees for the least amount of time required for their processing, transfer, release or repatriation as appropriate and operationally feasible,” said the CBP spokesperson.

VICE spoke to Dr. Sierra about why she’s volunteering to help people in CBP custody and how holding migrants for any amount of time without offering vaccines and other medical care can result in deaths.

VICE: How did you get involved with the letter and why were you compelled to do so?

Julie Sierra: Doctors for Camp Closure organized an event in Washington D.C., where we marched in a rally and met with congressional representatives to talk about our demands that the camps be closed, that asylum seekers not be put in detention centers at all. One of the doctors that was at that event had reviewed the autopsy reports from multiple kids who've died in CBP custody and found that three of them had died of complications of the flu. We were talking about how flu season is coming up, and we know that they're not getting vaccinated. So we wanted to have an action to demand that they let us do that: vaccinate people in detention.

How did you expect CBP to respond?

Well, I think we were all pretty sure that they were going to say no, but we were hoping that they would say yes because we're offering to provide the flu vaccines and provide doctors who are voluntarily going to go into the detention centers and give the actual vaccinations. We thought How can they deny it if it's not going to cost them anything?

Why did you expect them to say no?

I interact with Border Patrol a lot because I work on both sides of the border with asylum seekers with this group called Refugee Health Alliance. They just don't even see these people as human, so they don't care. Even though, you know, three kids have died. It's like, what does it take for you to actually acknowledge that you need to do something to prevent illness?

My impression was that they just don't feel like it's their responsibility because they have people for such a short period of time, but the problem is they're keeping people in conditions that greatly increase their risk of getting sick with the limited hygiene.

Why is it so important that people in CBP custody get the flu vaccine, even if they are only there for 3 days? Though we know it’s often much longer.

I work at a shelter on the San Diego side [of the border] sometimes and we see people that are being dropped off from the detention centers, and they all tell us the same thing: that they aren't allowed to bathe, they aren't given soap, the lights are on 24 hours a day, they're sleeping on cold hard floors. And all of them are in close quarters. If you want to get people sick, that's how you do it.

Once [migrants] get taken into [CBP] custody, they're only there for three to five days, which is the perfect opportunity to vaccinate them, because then they all go across the country. So if they're getting sick from the flu, they're basically spreading it everywhere.

So you’re saying that no matter how long migrants are in custody, detaining people in poor conditions without giving them vaccinations like the flu shot is dangerous?

Absolutely. Anytime you have a large group of people in a confined space, and without proper hygiene, you're going to have all kinds of viruses passing from one person to another, and we're expecting this flu season to be quite bad. So not vaccinating people absolutely puts them at high risk of getting sick and of complications of the flu and even potentially death. A lot of these migrants have been in close quarters for quite some time. If we could just go into the detention centers where we know where they are and vaccinate them, it would save a lot of potential illness and complications.

So CBP refused the help, what now?

We are currently trying to come up with some action plans that we can do, whether that be a protest, a demonstration, or further pressure on Border Patrol. We're not gonna let it fall through the cracks because of the potential catastrophe waiting to happen. There's 2,000 of us now in this organization all over the country, and we're like, we'll do it for free. Let us in and let us take care of people.