"Say goodbye to your smile and say hello to polio - that's what's on the horizon if Robert F. Kennedy Jr. becomes the Secretary of Health and Human Services." Elizabeth Warren has said

Aaron Siri, a lawyer who represented Robert F. Kennedy Jr. during his presidential campaign, is now helping him select candidates to lead the Health and Human Services Department (HHS) under President-elect Donald Trump. Kennedy, known for his skepticism about vaccines, was nominated by Trump to head the HHS after suspending his campaign and endorsing Trump.

Siri, who has a history of challenging vaccine approvals and mandates, is reportedly assisting Kennedy in vetting candidates for top positions in the department, according to The New York Times. Before his involvement in Kennedy’s campaign, Siri filed a petition in 2022 on behalf of the Informed Consent Action Network (ICAN) requesting that the Food and Drug Administration (FDA) revoke its approval of the polio vaccine. ICAN, founded by Del Bigtree—who also served as Kennedy’s campaign communications director—is widely regarded as anti-vaccine.

This petition was not an isolated incident. Siri has also filed requests to revoke the approval of the hepatitis B vaccine and to pause the distribution of 13 other vaccines, the Times reported. He has challenged vaccine mandates in court, with some successes, particularly related to COVID-19 vaccines.

The 2022 petition against the polio vaccine claimed the clinical trials lacked a proper control group and only monitored safety for three days post-injection, failing to meet standards for proving safety before licensure. These claims have added fuel to the broader debate about the ethics of placebo use in clinical trials. While some argue that placebo use is vital for assessing safety and efficacy, others contend it is unethical when effective treatments already exist.

Polio, a highly infectious and potentially deadly disease, caused widespread devastation before vaccines were developed. According to the World Health Organization, polio killed or paralyzed over half a million people annually worldwide before the introduction of vaccines in the 1950s. After the vaccine’s release, annual U.S. cases plummeted from 58,000 to just 161 by 1961.

Sanofi, the manufacturer of the polio vaccine named in Siri’s petition, stated that more than 280 million people worldwide have received the vaccine, which has been evaluated in over 300 studies with safety follow-ups extending to six months.

Neither Siri’s law firm, Siri & Glimstad, nor Kennedy’s team responded immediately to Fortune’s request for comment. Siri told the Times that the petitions were filed on behalf of his clients. A spokesperson for Kennedy clarified that Siri has been advising Kennedy but has not discussed his vaccine-related petitions with any HHS nominees. “Mr. Kennedy has long advocated for transparency in vaccines and the right to informed choice,” the spokesperson told the Times.