Marcia, Marcia, Marcia is absolutely mad about the measles outbreak. Specifically, that anti-vaxxers are using her image to promote their cause.

A 1969 episode of the classic sitcom, "The Brady Bunch," titled "Is There a Doctor in the House?" has found itself at the center of the controversy over the measles vaccine. The show features all six Brady kids coming down with the disease, and Marcia, the oldest daughter, cheerfully declaring, "If you have to get sick, sure can't beat the measles."

Maureen McCormick, the actress who played Marcia, said she became furious after learning that people critical of vaccines have repeatedly used the episode to illustrate that measles are harmless.

"It's really wrong when people use people's images today to promote whatever they want to promote and the person's image they're using they haven't asked or they have no idea where they stand on the issue," McCormick told NPR.

Maureen McCormick said she did not want a 50-year-old episode of "The Brady Bunch" to be used in 2019 to bolster arguments against vaccines. Gregg DeGuire

McCormick, who said her own child has been vaccinated against the disease, said she came down with measles as a child and it was nothing like the "Brady Bunch" episode. Instead, she got really sick.

"Having the measles was not a fun thing," she said. "I remember it spread through my family."

The United States is experiencing its worst measles outbreak since the disease was declared eliminated in the country in 2000. According to the Centers for Disease Control and Prevention, 695 cases have been reported across 22 states.

Last week in California, nearly 1,000 students and faculty members at two universities in Los Angeles were quarantined after concerns they had been exposed to the measles on campus. Hundreds were eventually cleared after they proved that they had been vaccinated.

Medical experts have been trying to stress the importance of getting immunized — and the need to separate fact from fiction.

"It's common for a lot of people to think about vaccine-preventable childhood illnesses as mild and just a part of growing up, and for a lot of people that's definitely true," Dr. Natalie Azar, an NBC medical contributor, said. "But untreated measles can lead to life-threatening complications."

Another person unhappy with how "The Brady Bunch" is being used by the anti-vaccine movement is Lloyd Schwartz, who is the son of the show's creator, Sherwood Schwartz. He says his father would be opposed to what's happening, especially since he had all of his children vaccinated.