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.