"Quite apart from the health benefits and risks associated with using or not using vaccines, some people oppose the use of certain common vaccines—such as Varivax (for chicken pox) and Meruvax II (for rubella)—because of the connection between the production of these vaccines and elective abortion. The production of these and some other vaccines involves a stage in which viruses are grown in human cell culture. Because viruses can reproduce only inside living cells, they are placed in the human cell culture and allowed to grow in large quantities. The viruses are removed from the cell culture, inactivated or modified, and then processed further in order to produce the vaccine. There are two human cell lines that provide the cell cultures needed for producing vaccines. One of these lines, called WI-38, was developed in 1961 in Philadelphia from the normal lung tissue of a three-month-old female fetus obtained by surgical abortion.19 The other line, called MRC-5, was developed from normal lung tissue of a fourteen-week-old male fetus, aborted “for psychiatric reasons.” The WI-38 human diploid cell line … has been shown to have one of the broadest human virus spectra of any cell population that has been tested and is especially useful for isolation of rhinoviruses. The cells are free of contaminating viruses, mycoplasmas or any other microorganism and do not form tumors when inoculated subcutaneously into terminal human cancer patients.21 MRC-5 cells replicate more rapidly and are less sensitive to adverse environmental factors than WI-38 cells. The MRC-5 cell line, like WI-38 (ATCC CCL-75), is susceptible to a wide range of human viruses, is suitable for the production of viral vaccines, and has been useful in senescence studies."