As a measles outbreak spreads across West Texas, Dr. Ana Montanez is fighting an uphill battle to convince some parents that vitamin A - touted by vaccine critics as effective against the highly contagious virus - will not protect their children.

The 53-year-old pediatrician in the city of Lubbock is working overtime to contact vaccine-hesitant parents, explaining the grave risks posed by a disease that most American families have never seen in their lifetime - and one that can be prevented through immunization.

Increasingly, however, she also has to counter misleading information. One mother, she said, told her she was giving her two children high doses of vitamin A to ward off measles, based on an article posted by Children's Health Defense, the anti-vaccine group led by Robert F. Kennedy Jr. nearly a decade before he became President Donald Trump's top health official.

"Wait, what are you doing? That was a red flag," Montanez said in an interview. "This is a tight community, and I think if one family does one thing, everybody else is going to follow. Even if I can't persuade you to vaccinate, I can at least educate you on misinformation."

Kennedy resigned as chairman of Children's Health Defense and has said he has no power over the organization, which has sued in state and federal courts to challenge common vaccines including for measles.

The organization did not respond to a request for comment.

As U.S. health and human services secretary, Kennedy has said vaccination remains a personal choice. He has also overstated the evidence for use of treatments such as vitamin A, according to disease experts.

The supplement does not prevent measles and can be harmful to children in large or prolonged doses, according to the American Academy of Pediatrics. It has been shown to decrease the severity of measles infections in developing countries among patients who are malnourished and vitamin A deficient, a rare occurrence in the United States.

"I'm very concerned about the messaging that's coming out," said Dr. Jeffrey Kahn, chief of infectious diseases at Children's Health in Dallas. "It's somewhat baffling to me that we're relitigating the effectiveness of vaccines and alternative therapies. We know how to handle measles. We've had six decades of experience."

Andrew Nixon, a Department of Health and Human Services spokesperson, did not respond to questions about Kennedy's handling of the measles outbreak. But commenting on a measles-related death in New Mexico, Nixon said on Thursday that the U.S. Centers for Disease Control and Prevention "recommends vaccination as the best protection against measles infection."

Texas officials said on Friday that the state's measles outbreak had grown to 198 cases, including 23 people who were hospitalized. That includes the death of an unvaccinated school-age child at a Lubbock hospital last month.

New Mexico officials have tallied 30 cases and one death of an unvaccinated adult. Those are the first deaths from measles in the United States since 2015.

'I'M WILLING TO HOLD OFF'

A 29-year-old nurse who is the mother of three and is a self-described Kennedy fan visited Montanez's clinic on Thursday. She asked to be identified as Nicole C. - her middle name and last initial - to protect her family's privacy.

She said she values the doctor's advice and appreciated that she never felt judged for not fully vaccinating her school-age daughter and toddler twins - a boy and a girl - with a second dose of the measles, mumps and rubella vaccine.

After the initial shots, she said she grew more concerned about potential side effects from vaccines and embraced more natural supplements.

She said school officials told her that her daughter would have to miss 21 days of class if she remains under-vaccinated and was exposed to measles.

The risk of contact in Lubbock is real. Montanez called about a dozen families last month because they were exposed to measles in her own waiting room, which she shares with other doctors in the Texas Tech physicians group.

Still, Nicole could not go through with the vaccination during her visit this week. She said she and her husband had prayed about it and believed in their family's God-given immune systems.

"As a mom, you naturally think, 'Oh my goodness, I can't let my daughter miss 21 days of education.' But who knows what effects the vaccine could cause? That could be a lifetime of issues. I'm willing to hold off on the shot," she said.

Public health experts have said vaccines for measles and other diseases pose minimal risks of side effects and protect children and adults against diseases that once routinely killed many people.

As flu season worsened this winter, Nicole said she started giving her children a daily dose of strawberry-flavored cod liver oil, which is high in vitamin A, based on information other mothers had shared with her.

Montanez took her vaccine rejection in stride. The doctor said she has persuaded more than a dozen parents to get their children fully vaccinated in recent weeks.

"I think that leaving her and her family enough space to make their own decisions - and being available for any questions - is really my goal," Montanez said. "My hope is that at some point she's going to call me and say, 'Can we go and get the vaccine?'"