A sizeable number of U.S. millennials, the age group between 24-39, agree with at least some of the ideas promoted by the anti-vaccination movement.

Of millennials surveyed, 55% claim not to have gotten a flu shot in the last year, and 61% believe at least one claim made by anti-vaccination activists, according to a study conducted by the American Academy of Family Physicians.

More than 20% of American men said they did not get a flu shot because they don't view it as a serious illness, compared to only 5% of women who don't believe the flu is worth preventing.

Dr. Alexa Mieses told NBC that younger Americans opting for urgent care instead of forming long-term care relationships with a physician is "very alarming."

"I personally have seen a lot of mistrust around the flu shot in my one-on-one interactions taking care of patients," Mieses told NBC. "We absolutely have to acknowledge the way in which the medical system exploited African Americans in the past that now contributes to a feeling of mistrust."

The numbers varied along demographic lines, with 9 out of 10 Asian Americans saying they believed the flu shot was important to protect against sickness, while more than 60% of black respondents voiced concerns about vaccination.

A Gallup poll released this week found that 10% of respondents believed that vaccines could potentially cause autism, up 4 percentage points from the last poll taken in 2015.