Amid a tense line of questioning during the first day of confirmation hearings, Robert F. Kennedy Jr. said he would keep his financial stake in pending litigation centered on Gardasil, a vaccine meant to prevent cervical cancer, which can be caused by the human papillomavirus, or HPV.
On Thursday, under questioning by Senator Patty Murray, Democrat of Washington, Mr. Kennedy declined to disavow comments he had made disparaging the vaccine as unsafe and as something that no parent should give to a child. (Unexpectedly, he also seemed to assert that he had surrendered his financial stake in the litigation.)
Mr. Kennedy has often singled out Gardasil in his critiques of vaccines, suggesting that its ingredients increase the risk of cancer, lead to autoimmune conditions and may be responsible for a rise in mental illness.
The Children’s Health Defense, a nonprofit co-founded by Mr. Kennedy, called the vaccine “one of the most dangerous vaccines ever approved.”
The Centers for Disease Control and Prevention, which monitors the side effects and ongoing safety of vaccines like Gardasil, disagrees with that characterization, noting that the body of scientific evidence “overwhelmingly supports their safety.”
Before the Gardasil vaccine was approved by federal regulators in 2014, it underwent lengthy clinical trials with more than 15,000 participants.
C.D.C. monitoring has revealed some minor side effects, most commonly dizziness, nausea, headache and fever. And in extremely rare cases, there have been more serious side effects documented, like Guillain-Barré syndrome.
But the vaccine is also remarkably effective at preventing cancer — roughly 97 percent effective in preventing cervical cancer, and nearly 100 percent effective in preventing external genital warts.
The C.D.C. is currently conducting research into the relationship between all vaccinations and certain conditions like postural orthostatic tachycardia syndrome (POTS) and chronic fatigue syndrome.
But current studies show that HPV vaccines cause “no increased risk” of chronic fatigue syndrome and do “not support a causal link” between Gardasil and POTS.
