What Clarence Thomas said about fetal cell lines and COVID-19 vaccines

Supreme Court Justice Clarence Thomas wrote in a dissenting opinion that genetic materials derived from abortions were used in the development of the COVID-19 vaccines.

Thomas' June 30 opinion came after the U.S. Supreme Court declined to hear a challenge to New York's COVID-19 vaccine mandate for health care workers.

"Petitioners are 16 health care workers who served New York communities throughout the COVID-19 pandemic," Thomas wrote. "They object on religious grounds to all available COVID-19 vaccines because they were developed using cell lines derived from aborted children."

PolitiFact has fact-checked many claims about the COVID-19 vaccines, including one that falsely said that the Oxford-AstraZeneca vaccine contains aborted fetal tissue. Thomas’ description of the plaintiff’s position was more carefully worded and did not claim that fetal tissue is an ingredient in the vaccines.

Instead, he focused on the development of the vaccines and the use of "cell lines."

Thomas did not specify whether the "cell lines" were used in the vaccines’ testing phase or in final production. However, the complaint denied by the Supreme Court said that all of the COVID-19 vaccines used in the U.S. "employ aborted fetus cell lines in their testing, development, or production." (We’re not rating Thomas’ statement on our Truth-O-Meter because Thomas was describing the plaintiff’s legal argument.)

Several media outlets mistakenly misinterpreted the opinion, believing Thomas claimed the vaccines contain fetal cells. The outlets also focused on Thomas’s use of the words "aborted children," a provocative phrase that doesn’t align with how the medical community describes an aborted fetus. 

Fetal cell lines have been used to test and develop vaccines since the 1960s. They are made by isolating cells from fetal tissue, in some cases from an aborted fetus. These cell lines can be cloned indefinitely and used for medical research. 

Vaccines for chickenpox, rubella and shingles also are developed using fetal cell lines.

The vaccines from Moderna, Pfizer and Johnson & Johnson are currently the only three authorized for use in the U.S. Of the three companies, only Johnson & Johnson uses fetal cell lines to produce its vaccine.

The Johnson & Johnson vaccine uses the company’s own proprietary fetal cell line called PER.C6, derived from retinal tissue from an 18-week-old fetus aborted in 1985.

The vaccine uses a modified cold virus known as an adenovirus that can train the body to recognize the coronavirus. The adenovirus is grown and replicated in the PER.C6 cell line, purified of the cells and formulated into the vaccine.

By the time it’s administered, the vaccine contains only trillionths of a gram of DNA from the cell line.

The use of fetal cell lines in Johnson & Johnson’s vaccine has raised moral objections among some Catholics and anti-abortion advocates.

The Vatican’s Congregation for the Doctrine of Faith said in 2020 that "it is morally acceptable to receive COVID-19 vaccines that have used cell lines from aborted fetuses in their research and production process."

However, some Catholic bishops considered Johnson & Johnson’s vaccine "morally compromised" and encouraged the use of the Moderna and Pfizer vaccines instead.

Those two vaccines were developed with messenger RNA, or mRNA, technology, which uses spike proteins from the coronavirus SARS-CoV-2 rather than a modified cold virus. Fetal cell lines were not used to manufacture Moderna and Pfizer vaccines. But the companies used fetal cell lines as part of their development to test whether their vaccines were safe and effective in humans.

The U.S. Conference of Catholic Bishops issued a statement in 2020 saying the use of fetal cell lines for testing made the Moderna and Pfizer vaccines more palatable.

"In view of the gravity of the current pandemic and the lack of availability of alternative vaccines," the statement said. "The reasons to accept the new COVID-19 vaccines from Pfizer and Moderna are sufficiently serious to justify their use, despite their remote connection to morally compromised cell lines."