Jessica Biel joined notorious anti-vaxxer Robert F Kennedy Jr in lobbying against a California vaccination bill Tuesday - but then insisted she's not against the shots and instead supports families' right to decide.

The 37-year-old actress was labeled 'courageous' by activist Kennedy Jr after she met with 15 legislators at the California State Assembly and State Senate in Sacramento.

Pictured alongside the 65-year-old in a series of Instagram posts, mom-of-one Jessica urged lawmakers like Democratic Assemblywoman Autumn Burke to oppose SB 276, a bill limiting medical exemptions from vaccinations without approval from a state public health officer.

'[Jessica] is upset about this issue because of its particular cruelty. She has friends who have been vaccine-injured who would be forced to leave the state,' Kennedy - who's married to Cheryl Hines - explained to The Daily Beast on Wednesday.

Kennedy, who has sparked controversy in the past after using the word 'holocaust' to describe the number of children with autism in the US, thinks the new bill would force children to receive vaccinations.

He said: 'She was a very effective advocate. She was very strong and very knowledgeable. Extremely well-informed. An extremely effective advocate.'

Jessica Biel Timberlake, left, spent her Tuesday lobbying 15 legislators against supporting a California vaccination bill alongside Robert F. Kennedy Jr., right, at the California State Assembly and State Senate in Sacramento

Biel later posted on Instagram to say she is 'not against vaccinations' but is concerned with medical exemptions. It is believed Biel was referring to SB276 in her post

Jessica Biel is all smiles she arrives at LAX Wednesday. The 37-year-old actress was labeled 'courageous' by activist Kennedy Jr after she met with 15 legislators at the California State Assembly and State Senate in Sacramento

The Tufts University drop-out has never before spoken out against vaccines, but a source told In Touch back in 2015 that Biel 'refused to vaccinate' her son Silas Randall (now four) with husband Justin Timberlake (left, pictured April 27)

Kennedy Jr added: 'The biggest problem with the bill, which is something I think Jessica is concerned with is that a doctor who has made a determination - if he has found children in this state whose doctors have determined that they're too fragile to receive vaccinations - this bill would overrule the doctors and force them to be vaccinated anyways.'

He added: 'I would say that she was for safe vaccines and for medical freedom. My body, my choice.'

THE DEBUNKED SCIENCE USED IN ANTI-VAXXER BOOKS There are countless books that make anecdotal links between autism and vaccination, but they are all rooted on one now-debunked study. The 'scientific' root of the movement comes from a 1998 paper led by the now-infamous Andrew Wakefield - who has been dating Elle Macpherson. Wakefield's research suggested that the MMR (measles mumps and rubella) vaccine 'triggers' autism in children. In the scientific community, the backlash was swift and clear. Scores of scientists published their own studies in response, pointing out the poor quality of the study - for example, problems with the sampling, and unethical funding. Plus, most children develop the first signs of autism around the same age that they would get the MMR vaccine: between 12 and 18 months. Scientists pointed out there was no reason to think that shots caused autism - what Wakefield found was nothing more than a coincidence of timing. The Lancet, the journal that published the study, ultimately retracted it. But Wakefield's now-debunked research made headlines, and anti-vaccination sentiments spread like wildfire among some communities - including Hollywood. Advertisement

Biel later posted on Instagram to say she is 'not against vaccinations' but is concerned with medical exemptions.

She wrote: 'This week I went to Sacramento to talk to legislators in California about a proposed bill.

'I am not against vaccinations — I support children getting vaccinations and I also support families having the right to make educated medical decisions for their children alongside their physicians.

'My concern with #SB277 is solely regarding medical exemptions. My dearest friends have a child with a medical condition that warrants an exemption from vaccinations, and should this bill pass, it would greatly affect their family’s ability to care for their child in this state.

'That’s why I spoke to legislators and argued against this bill. Not because I don’t believe in vaccinations, but because I believe in giving doctors and the families they treat the ability to decide what’s best for their patients and the ability to provide that treatment.

'I encourage everyone to read more on this issue and to learn about the intricacies of #SB277. Thank you to everyone who met with me this week to engage in this important discussion!'

It is believed Biel was referring to SB276 in her post. SB277 was signed into law in 2015.

But those in favor of the bill say it would have little impact on those with valid reasons for not having the vaccinations.

Co-sponsor of the bill Leah Russin said: 'The children who need medical exemptions will not have a problem getting them if SB 276 becomes law.

'People who are on immuno-suppressant drugs will not have a problem getting a medical exemption—and in fact, the people who truly need medical exemptions desperately need everyone else to be vaccinated. That’s why they support this bill. Medical advice should be coming from medical professionals.

'A Hollywood celebrity and the head of an environmental organization should not have credibility on an issue about how to regulate the medical profession, when an overwhelming number of medical professionals support this bill.'

Kennedy's anti-vax post featuring Biel received congratulatory comments from former porn star Jenna Jameson, Golden Globe-nominated actress Rosanna Arquette, and James Van Der Beek's wife Kimberly.

The Tufts University drop-out has never before spoken out against vaccines, but a source told In Touch back in 2015 that Biel 'refused to vaccinate' her son Silas Randall (now four) with husband Justin Timberlake.

The source said: 'She feels that vaccination could cause complications'.

Measles strikes two new states as the caseload climbs over 1,000 On Monday it was revealed 21 more measles cases have been identified, bringing the total nationwide number to 1,022. The new cases have stretched into two more states Idaho and Virginia, making the total number of states affected up to 28. This means the 2019 outbreak is the worst since 1992, when 2,126 cases were recorded. The US is on track to lose its 'elimination' status and will instead become a country where measles is considered active. This year's outbreak has been attributed to vaccine misinformation and US parents who refuse to vaccinate their children. These parents believe, contrary to scientific evidence, that ingredients in the vaccine can cause autism. 'We cannot say this enough: Vaccines are a safe and highly effective public health tool that can prevent this disease and end the current outbreak,' Health and Human Services Secretary Alex Azar said in a statement last week. Advertisement

Kennedy told The Daily Beast: '[Jessica] is upset about this issue because of its particular cruelty. She has friends who have been vaccine-injured who would be forced to leave the state'

The Thimerosal: Let the Science Speak publisher claimed that the recent measles epidemic in New York and Washington State 'has almost nothing to do with unvaccinated children'

Kennedy, publisher of The Thimerosal: Let the Science Speak, is a notorious anti-vaxxer who has claimed the recent measles epidemic in New York and Washington State 'has almost nothing to do with unvaccinated children'.

He said: 'The measles epidemic has almost nothing to do with unvaccinated children. Particularly the medically-fragile children have nothing to do with it.'

The scientific consensus is that vaccines do not cause autism, but Robert also proudly chairs the Children's Health Defense - which alleges a government conspiracy that vaccines 'cause autism, ADHD, food allergies, cancer, and autoimmune diseases.'

In March he tweeted suggesting 'neurotoxins' in the HPV vaccine are making American teens mentally ill.

Jessica will likely join her 38-year-old singer husband this Thursday in Manhattan when he receives the Songwriters Hall of Fame's Contemporary Icon Award at the 50th annual induction ceremony inside Marriott Marquis Hotel.

Acting-wise, the Sinner star next plays American Public Radio reporter Lia Haddock in the 10-episode mystery Limetown, which starts streaming October 16 on Facebook Watch.

The scientific consensus is that vaccines do not cause autism, but Robert proudly chairs the Children's Health Defense - which alleges a government conspiracy that vaccines 'cause autism, ADHD, food allergies, cancer, and autoimmune diseases'

Kennedy's anti-vax post featuring Biel received congratulatory comments from former porn star Jenna Jameson, Golden Globe-nominated actress Rosanna Arquette, and James Van Der Beek's wife Kimberly