Fear could stop the coronavirus vaccine from reaching some of the people who need it most

A nurse gives a Covid-19 vaccine to a health care worker in Aurora, Colorado. As federal and state officials pin down details of how the vaccines will be distributed, immigrant advocates are expressing concerns.

(CNN)As vaccine distribution ramps up across the United States, advocates and public health experts are warning that more steps must be taken to make sure millions of undocumented immigrants have access to vaccines -- and aren't too scared to sign up.

"I'm very, very concerned," says Dr. Ranit Mishori, senior medical advisor for Physicians for Human Rights. "If we are as a country to achieve herd immunity, that means non-citizens who live among us have to be immunized."
Many undocumented immigrants live in communities that have already been hit disproportionately by the coronavirus, and many have a higher risk for exposure because they're essential workers on the frontlines, Mishori says. That, she says, makes it even more important for them to get vaccinated as quickly as possible.
But Mishori and other advocates and experts who recently spoke with CNN said a big obstacle is standing in the way of that goal: fear.
    Here are some of the key issues they're already seeing come up.

    She's started hearing concerns from her patients

    Dr. Kathleen Page says she's seen this fear play out time and time again during the pandemic. Sometimes, she says, undocumented patients are extremely ill with Covid-19, but still scared to go to the hospital because they're afraid they could end up in the hands of immigration authorities.
    And when it comes to the vaccine, Page says she's started hearing similar concerns from some of her patients.
    "I've heard from people who say, 'You know what, I'm not sure about this vaccine. I'm not sure whether to trust it, I don't trust this administration,'" says Page, an associate professor at Johns Hopkins University School of Medicine.
    Federal and state officials are still working out the details of how coronavirus vaccines will be distributed. It could be months before a vaccine is available even for some essential workers, let alone members of the general public. And a new administration that's vowed to swiftly change immigration policies is waiting in the wings.
    But already in some corners of the immigrant communities that have been disproportionately devastated by the pandemic, Page says, vaccine conspiracy theories are taking hold. She says it's not hard to understand why skepticism and mistrust of the government are prevalent in undocumented communities -- and why some immigrants fear that data collected when vaccines are given could later be used by immigration authorities.
    "It doesn't take a lot," she says, "to convince someone who has seen things like families separated at the border, kids separated from their parents, to think, 'Well, this government Is not looking out for me, and why should I trust them?'"
    Page says she tells her patients she'll be taking the vaccine, and she hopes they'll do the same.
    But she says the concerns she already sees bubbling up are a clear sign that community leaders must be involved in the vaccine rollout.
    "We need to get enough people to really trust the system and get access and get vaccinated so we can make a difference," she says. "Otherwise this group of people will continue to be suffering disproportionately."
    Asked by CNN whether -- and how -- vaccines would be made available to undocumented immigrants as part of the federal government's distribution efforts, the Department of Health and Human Services issued a statement saying it was "not involved with this policy decision" and is working to make sure every American has access to the vaccine. State and local governments will ultimately decide on how vaccines are distributed, HHS said.
    "Operation Warp Speed will deliver vaccines to administration sites requested by jurisdictions, enabling and executing their plans, as they best know their populations and areas," the statement said, referring to the federal vaccination effort.

    Worries about cost could also get in the way