"Cells derived from elective abortions have been used since the 1960s to manufacture vaccines, including current vaccines against rubella, chickenpox, hepatitis A, and shingles. They have also been used to make approved drugs against diseases including hemophilia, rheumatoid arthritis, and cystic fibrosis. Now, research groups around the world are working to develop more than 130 candidate vaccines against COVID-19, according to the World Health Organization; 10 had entered human trials as of 2 June. At least five of the candidate COVID-19 vaccines use one of two human fetal cell lines: HEK-293, a kidney cell line widely used in research and industry that comes from a fetus aborted in about 1972; and PER.C6, a proprietary cell line owned by Janssen, a subsidiary of Johnson & Johnson, developed from retinal cells from an 18-week-old fetus aborted in 1985. Both cell lines were developed in the lab of molecular biologist Alex van der Eb at Leiden University. Two of the five vaccines have entered human trials (see table, below). In four of the vaccines, the human fetal cells are used as miniature "factories" to generate vast quantities of adenoviruses, disabled so that they cannot replicate, that are used as vehicles to ferry genes from the novel coronavirus that causes COVID-19. When the adenoviruses are given as a vaccine, recipients' cells begin to produce proteins from the coronavirus, hopefully triggering a protective immune response. The fifth vaccine, which has shown promise in monkeys and is headed for human trials as soon as this summer, is what is known as a protein subunit vaccine. Researchers at the University of Pittsburgh use HEK-293 cells to manufacture the coronavirus' spike protein—a vital part of its structure—which is used to trigger an immune response. The vaccine is delivered through a skin patch with 400 tiny needles. The fetal cell lines are key to producing both types of vaccine. "HEK-293 [cells] are essential for making protein subunit vaccines," says Andrea Gambotto, a vaccine scientist at the University of Pittsburgh School of Medicine and the vaccine's lead developer. Their human origin is important, he says: "Cultured [nonhuman] animal cells can produce the same proteins, but they would be decorated with different sugar molecules, which—in the case of vaccines—runs the risk of failing to evoke a robust and specific immune response." (Among the developers of the five vaccines, only Gambotto responded to a request for comment.)"