The health and human services secretary, Robert F. Kennedy Jr., aired another controversial view on vaccines on Wednesday, saying that the ongoing measles outbreak in Texas hit some religious communities because the MMR vaccine “contains a lot of aborted fetus debris and DNA particles.” It’s the latest incident of Mr. Kennedy muddying the waters of the vaccines debate, delighting his supporters and frustrating the public health establishment.

Speaking with Chris Cuomo, Mr. Kennedy commended the Trump administration’s response to the measles outbreak, saying, “Our numbers have plateaued.” According to the Centers for Disease Control and Prevention, there are currently 884 confirmed measles cases in the United States, 663 of which are in Texas.

“There are populations in our country, like the Mennonites in Texas, who are most afflicted and they have religious objections to the vaccine,” Mr. Kennedy said. “Because the MMR vaccine contains a lot of aborted fetus debris and DNA particles, so they don’t want to take it,” he added.

Mr. Kennedy continued his criticism of the media coverage of the measles epidemic, saying it overshadowed the rise in autism cases that he believes is a more pressing matter. 

“Autism in 1970 was one in 10,000 Americans,” he said on NewsNation. “Today, it’s one in 31. In California, it’s one in every 20 kids, one in every 12.5 boys. This is what the media ought to be focusing on, and it’s not,” Mr. Kennedy said.

During a separate town hall with a TV personality Dr. Phil, on Monday, Mr. Kennedy said the efficacy of the MMR vaccine, which prevents measles, is “ultimately going to wane,” before stopping himself to say that “the HHS continues to recommend that vaccine.” 

Mr. Kennedy, a longtime vaccine skeptic, has at times toned down his rhetoric on vaccines, though he has encouraged parents to “do their own research” when it came to vaccinating their children. 

Mr. Kennedy’s comment about fetal cells is not baseless. Many vaccines, like the MMR vaccines, are made by growing the virus in fetal cells because these cells are very unlikely to contain a virus, making the vaccines safer. The medical community says that the final vaccines themselves do not contain cells or pieces of human DNA, according to the Children’s Hospital of Philadelphia’s Vaccine Education Center.

“Once the vaccine virus is grown, it is purified, so that cellular debris and growth reagents are removed,” according to the Children’s Hospital of Philadelphia. 

Some religious groups are unconvinced that the vaccines are cleansed of such cells, and regardless, they are troubled that fetal cells were used at all in creating the vaccines. 

Measles is a highly contagious respiratory illness that spreads through coughing and sneezing and, in its pre-vaccine heyday, would routinely infect small children. The fatality rate is low — about one in 1,000 — something vaccine opponents routinely cite. The disease was considered eradicated from the United States in 2000 because of the MMR vaccine, which is administered as part of the suggested childhood immunization schedule for children ages 1 to 4 years, according to Northwestern Medicine.