Years before this year's anti-mask and reopening demonstrations, vaccine opponents were working on reinventing their image around a rallying cry of civil liberties and medical freedom.

Now, boosted by the pandemic and the political climate, their rebranding is appealing to a different subset of society invested in civil liberties — and, some health officials say, undercutting public health efforts during a critical moment for vaccines.

A new analysis from several institutions has found that between 2009 to 2019, conversations around civil liberties in the anti-vaccine community had increased, with Facebook pages framing vaccines as an issue of values and civil rights.

Researchers reviewed over 200 Facebook pages supporting vaccine refusal for their paper published in the American Journal of Public Health this month. David A. Broniatowski, the paper's lead author, said current protests against government lockdowns and masks took their pages directly from the anti-vaccine playbook.

“We could’ve seen it coming,” said Broniatowski, an associate professor at George Washington University's School of Engineering and Applied Science. “This was all happening right under our noses, and it’s continuing to happen.”

In recent weeks, protesters gathered in Massachusetts to demonstrate against the governor’s mandate requiring schoolchildren to receive the influenza vaccine. In Facebook pages and groups touting medical freedom and vaccine choice, the protesters have called the mandate unconstitutional and say it infringes on their rights.

Anita Garcia has been protesting vaccines for years and recently took part in protests against the flu mandate in Massachusetts, where she is from. Garcia is a member of an 866-member Facebook group called “Massachusetts for Medical Freedom.” She said that with the flu mandate demonstrations, she is seeing protesters turn out to object to what they consider government overreach.

“All you can do is try to fight for your freedom,” Garcia said. “We are for medical freedom, bodily autonomy. Our bodies are ours, not for someone else to govern.”

Vaccines, though, save lives — 2 to 3 million a year, according to World Health Organization estimates. And vaccines have all but eliminated from American life such childhood diseases as measles, which regularly infected 3 to 4 million people a year in the United States before a vaccine was developed. It was declared eliminated from the United States in 2000, though low vaccination rates in some communities have led to outbreaks in recent years.

Vaccines are encouraged, or in some cases required, because they have been proven safe and protect not only those vaccinated but also others who can't be by slowing the spread of preventable diseases.

Historically, the anti-vaccine community has been known for its concerns around vaccine safety and the debunked theory that vaccines cause autism. Broniatowski and researchers found, though, that civil liberties have emerged as a common narrative among vaccine refusal pages on Facebook, including those who also supported alternative medicine and conspiracy theories about the pharmaceutical industry and billionaire philanthropist Bill Gates.

The rebranding to emphasize liberties is allowing vaccine opponents to exploit American reactions to the pandemic, said Dorit Reiss, a University of California Hastings law professor who specializes in policy issues related to vaccines.

“I do think we are seeing an increase in people in support of them just because more people are vulnerable, upset and distrustful," Reiss said. “And the anti-vaccine movement knows exactly what to say."

“Medical freedom” advocates are moving quickly on social media to capitalize around the frustration around the pandemic. During this month's vice presidential debate, Democratic Sen. Kamala Harris was asked if she would take a coronavirus vaccine. Harris responded by saying she'd take the vaccine if public health professionals recommend it — but that “if Donald Trump tells us we should take it, I’m not taking it.”

Shortly after her remark, accounts and pages on Facebook and Twitter that support medical freedom began circulating a text post that said “Kamala won’t take a vaccine that DJT pushed. Imagine being forced to take a mandated vaccine from a leader you disagree with!! The irony. Do you NOW understand what Medical Freedom means?”

“You can see the consequences to these groups sowing distrust around vaccines. And they really matter, and they are going to come out in this pandemic,” said Mark Dredze, associate professor of computer science at Johns Hopkins University and one of the paper’s authors.

In May, a poll from The Associated Press-NORC Center for Public Affairs Research found that 31 percent of Americans were unsure if they would get the COVID-19 vaccine once released.

Medical freedom supporters are pushing out their message to a significant portion of Americans who are not anti-vaccine but who are witnessing the politicization of the virus and have concerns about the vaccine, said Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston.

“Children have a fundamental right to access to vaccines," said Hotez, who is also co-director of the Texas Children’s Hospital Center for Vaccine Development. “You need a high percentage of vaccine coverage in order to achieve herd immunity to protect all children."

As public health officials fight the pandemic and groups push for the economy to reopen, one expert suggests that health professionals trying to find common ground are going to have to meet people where they are.

“You can’t have a system that will result in us no longer being able to protect our communities from measles because we allow so much of the choice to occur that vaccine rates plummet,” said Ross D. Silverman, professor of health policy and management at Indiana University. “There is an alchemy there.”

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Beatrice Dupuy is a journalist on The Associated Press' news verification team. Follow her on Twitter at http://twitter.com/Beatrice_Dupuy