They claim to use Human Embryonic Kidney (HEK) cells 'harvested' from a female fetus in the 1970s to 'produce' or 'test' the vaccine. They do not acknowledge that the vaccines could contain HEK cells.
However, vaccines have been made with monkey kidney cells and were found to have been contaminated with simian (monkey) virii:
"There is no dispute that millions of Americans received polio vaccines that were contaminated with the virus called Simian Virus 40, or SV-40."
https://www.govinfo.gov/content/pkg/CHRG-108hhrg91047/html/CHRG-108hhrg91047.htm