evidence: Two of the most commonly used cell strains in vaccine development or manufacturing are MRC-5 and WI-38, which were made decades ago from lung tissue taken from two different aborted fetuses in the U.K. and Sweden in the 1960s. Researchers discovered the cells were useful for the purpose because they were good at growing viruses that infect humans, and many vaccines are made of weakened viruses. [...] Other vaccines produced in fetal cell lines include chickenpox, hepatitis A and one of the rabies vaccines. As the Children’s Hospital of Philadelphia has explained, vaccines manufactured in fetal cell lines do not contain any of the cells because the vaccines are purified. [...] The Pfizer/BioNTech and Moderna vaccines, which do not contain virus and instead are made of messenger RNA, have a more tenuous link to fetal cell lines. Neither vaccine is made in such cells, but both companies did certain experiments testing their vaccines in HEK-293T cells, which are commonly used in biomedical research.