Five years ago, hundreds of people crowded the halls of the state Capitol protesting legislation that sought to tighten California’s vaccine rules. Outside, music blasted something about a revolution and people carried signs that read “Vaccine mandates violate bodily autonomy.”From the sea of red-clad protesters emerged a familiar face idolized by the anti-vaccine activists: Robert F. Kennedy Jr.

He was the guest of honor in one of the biggest public health showdowns the state has seen in recent years. Ultimately, he and his followers lost — the Legislature passed a law to clamp down on fraudulent or inappropriate medical exemptions for required childhood vaccines.

Today, Kennedy finds himself on a bigger stage with potentially far more influence and power. President-elect Donald Trump has nominated the former environmental lawyer turned controversial vaccine critic to oversee the nation’s health policy as secretary of Health and Human Services.

He has been known to make false, and at times dangerous, claims about medicine and public health. Perhaps most infamously he linked vaccines to autism — a claim that has been debunked over and over again.

Now with Kennedy in the running to lead the federal health department, health leaders and advocates in California and across the country are voicing their concerns and preparing to combat a potential wave of medical disinformation.

Having a vaccine skeptic at the helm of the U.S. Health and Human Services agency, some say, could lead to more Americans refusing to be vaccinated and potentially put lives at risk. It could also embolden the anti-vaccine movement in California.

Dr. Richard Pan, a pediatrician who as a state senator authored the 2019 medical exemption law and a separate law that eliminated personal belief exemptions for childhood vaccines, said having a health secretary who casts doubt on vaccines is “a danger” and “disturbing.”

“I imagine we’re going to see a lot more direct attacks on individual scientists, individual people. I’m anticipating that I’m probably gonna be hoisted somewhere by those guys as well. I don’t think RFK Jr. has forgotten about me yet,” he said.

Pan said he’s met Kennedy twice when Kennedy traveled to Sacramento to oppose his bills.

Carrying those laws made Pan the subject of harassment and attacks, and at one point an anti-vaccine activist shoved him while Pan was walking in a Sacramento street. At protests, anti-vaccine activists plastered Pan’s face on posters with the word “LIAR” in red letters.

Now, people who rallied against his vaccine bills are celebrating Kennedy’s potential spot on Trump’s cabinet, and calling for “justice” via social media posts.

In one of their last quarrels, Pan publicly called for Kennedy to be banned from social media platforms when Kennedy promoted COVID disinformation. In response, Kennedy told the Sacramento Bee that Pan’s request for censorship was anti-American.

More recently, Kennedy has taken a more measured approach when responding to questions about vaccines. Following Trump’s win he told NBC News that he isn’t looking to take vaccines off the market, but rather is advocating for informed choice.

“If vaccines are working for somebody, I’m not going to take them away,” he said.

What can RFK Jr. do as health secretary?

If Kennedy is confirmed as head of Health and Human Services, he would oversee a $1.7 trillion budget and about a dozen agencies. He would be responsible for managing pandemic preparedness, and would be in charge of issues ranging from health insurance to food safety.

Experts say that any controversial changes would likely be met with litigation that could slow or derail Kennedy’s proposals. Still, there are several ways anti-vaccine sentiment in the federal government could undermine public health gains in states.

For example, school immunization mandates are issued by states and while the federal government cannot directly change those, it could decide to withhold public health funding, such as grants sent to states to help fund vaccination efforts, said Dorit Reiss, a professor at UC Law San Francisco.

As health secretary, Kennedy would also have the power to appoint members of an advisory committee that makes recommendations on immunization practices to the U.S. Centers for Disease Control and Prevention.

Reiss added that the health secretary also has the power to expedite or limit access to new vaccines, which would become especially important in the case of another pandemic.

It is the secretary of Health and Human Services who declares a public health emergency and issues emergency use authorization for unapproved vaccines. When COVID shots were first made available to the public in December 2020, they were allowed under this emergency designation. The U.S. Food and Drug Administration fully approved the vaccine for people 16 and older nine months later.

A secretary hostile to vaccines could block or remove the emergency use authorization. That means the vaccine manufacturer “would have to either apply for full approval at the moment or not sell the vaccine,” Reiss said.

Kennedy told NBC that he wouldn’t have “directly blocked” the emergency use of COVID-19 vaccines had he been secretary at the time, but rather would have made sure that “we have the best science.”

Yet at the height of the pandemic, Kennedy helped fuel mistrust of the coronavirus vaccine. In 2021, he called it the “deadliest vaccine ever made” in opposition to a Louisiana proposal that would have required school children to be vaccinated against the virus.

California vaccine mandates

In 2010, the California Legislature passed a law that added a booster of the pertussis vaccine, which protects against whooping cough, to the immunization schedule for teens to attend school. Catherine Flores Martin, the executive director of California Immunization Coalition, a nonprofit that advocates for vaccines, remembers when lawmakers were considering this bill, roughly about 18 people or so showed up in opposition, she said.

Fast-forward to 2015 and 2019, opposition to vaccine legislation evolved into mass protests of hundreds of people. “It’s gotten wild,” Flores Martin said.

“The vast majority of parents still vaccinate their children,” she said. “We hear a lot about hesitancy, but hesitancy doesn’t convert into not vaccinating.”

In the 2021-22 school year, 94% of California’s kindergarteners had received the required vaccines, the state’s public health department reported.

But Flores Martin acknowledges that it has become more challenging to pass vaccine legislation as opposition has become louder in California. She attributes this in part to the growing role of misinformation shared on social media platforms.

State public health officials did not respond to an interview request by deadline.

The year 2014 was notable in public health for a couple of reasons. That year whooping cough infections peaked, with more than 11,000 cases reported in the state, the most ever. Also, in December of that year, a measles outbreak at Disneyland contributed to the highest number of measles cases reported in the U.S. in two decades. Most of the cases were among unvaccinated children. The outbreak resulted in hospitalizations but no deaths were reported.

In California, the vaccine that protects against measles, mumps and rubella is among the required doses for kids to attend school. So is the polio vaccine and the Hepatitis B vaccine, among others. It was this measles outbreak that led the Legislature in 2015 to remove personal belief and religious exemptions for required shots.

Then in 2019, lawmakers came back and approved a second law that allowed the state’s Department of Public Health to review and revoke inappropriate medical exemptions. Medical exemptions have to be made by a physician and are reserved for small groups of people, such as those who are allergic to vaccine ingredients.

Following the 2019 law, ​​the rate of kindergarteners with medical exemptions decreased to the lowest levels since 2015-16, according to the state’s public health department. However, research shows that because of disruption in routine doctor visits during the pandemic, the number of kindergarteners who were not up to date on their immunizations ticked up.

Health advocates and experts say that it is now more important than ever to instill confidence in vaccines and proven public health measures. Flores Martin said doctors and health advocates will have to band together and push vaccine education to maintain high immunization rates. The messaging matters, she said.

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