U.S. Health and Human Services Secretary Robert F. Kennedy Jr. is facing widespread condemnation from medical experts and public health officials after repeating the debunked claim that the measles, mumps, and rubella (MMR) vaccine contains “aborted fetus debris” and DNA particles. Kennedy made the assertion during a televised NewsNation town hall.

Kennedy cited the supposed presence of “aborted fetus debris” in the MMR vaccine as a reason why some religious groups, such as the Mennonite community in Texas, object to vaccination.

“The claim that the MMR vaccine contains ‘fetal debris’ is not only scientifically inaccurate, it’s dangerously misleading,” Dr. Tyler Evans, former chief medical officer for New York City, told The Independent. “The rubella component of the MMR vaccine was developed decades ago using a well-established human cell line, replicated countless times. There is no actual fetal tissue in the vaccine. It’s time we stop politicizing science and return to evidence-based public health, because mistrust fueled by misinformation puts our most vulnerable communities at risk.”

The confusion stems from the fact that the rubella (German measles) component of the MMR vaccine is produced using a human cell line known as WI-38, which was originally derived from lung tissue from a single elective abortion performed in the 1960s. These cells have been replicated in laboratories for decades and are used as a growth medium for the virus. Importantly, the final vaccine product does not contain these cells or any fetal tissue. Instead, the vaccine is purified, and only the weakened virus and stabilizing agents remain.

While trace amounts of fragmented, biologically inert DNA from the cell line may be present, experts stress that these fragments are minuscule-measured in billionths or trillionths of a gram-and pose no health risk. The presence of such DNA fragments is not unique to the MMR vaccine and does not equate to the inclusion of “fetal debris” or tissue.

“It is not true that the vaccines have fetal elements, debris, cells in them,” Dr. Shira Doron, chief infection control officer for Tufts Medicine and hospital epidemiologist at Tufts Medical Center, told Health. “But what is true is that the viruses that need to be grown to create vaccines are grown in cells. In some cases, human cells.”

Major religious authorities, including the Vatican, have reviewed the use of vaccines developed with historical fetal cell lines and concluded that their use is morally permissible, especially when no alternatives exist and public health is at stake. The Catholic Church has encouraged the use of alternative vaccines when available but has stated that receiving such vaccines does not constitute cooperation with abortion.

Secretary Kennedy, long known for promoting vaccine skepticism before his appointment to lead HHS, has a history of making unsupported or debunked claims about vaccines, including alleged links to autism, questioning vaccine effectiveness, and misrepresenting vaccine safety data. FactCheck.org and other organizations have repeatedly addressed misleading statements made by Kennedy regarding vaccines and other health topics.

Kennedy’s remarks come amid a significant measles outbreak, particularly affecting communities with low vaccination rates. In Texas alone, hundreds of cases have been reported, with several deaths among unvaccinated children. Public health officials warn that misinformation about vaccine ingredients could further erode trust and worsen outbreaks.

Measles is a highly contagious disease that was declared eliminated in the U.S. in 2000 thanks to the highly effective MMR vaccine. As of May 1, 2025, the United States has reported a total of 935 confirmed measles cases across 30 jurisdictions, according to the CDC.

Most new vaccine trials in the United States already use placebos, meaning some participants receive the vaccine being tested while others receive an inert substance, like saline-to rigorously assess safety and efficacy. This approach is standard for vaccines targeting new diseases or pathogens for which no effective vaccine currently exists.

However, for vaccines against diseases where a safe and effective vaccine is already available (such as measles or polio), it is generally considered unethical to use a placebo group that would be denied proven protection. In these cases, new vaccines or updated formulations are typically tested against the existing vaccine rather than a true placebo, to avoid putting participants at unnecessary risk. For example, annual updates to flu and COVID-19 vaccines have usually been compared to prior versions or evaluated based on immune response, not through new placebo-controlled trials.