Vaccines Developed Using Human Cell Strains
The first vaccine created with the use of human cell strains was the rubella vaccine developed by Stanley Plotkin at the Wistar Institute in Philadelphia.
In 1941, Australian ophthalmologist Norman Gregg first realized that congenital cataracts in babies were the result of their mothers being infected with rubella during pregnancy. Along with cataracts, it was eventually determined that congenital rubella syndrome (CRS) could also cause deafness, heart disease, encephalitis, mental retardation, and pneumonia, among many other conditions. At the height of a rubella epidemic that began in Europe and spread to the United States in the mid-1960s, Plotkin calculated that 1% of all births at Philadelphia General Hospital were affected by congenital rubella syndrome. In some cases, women who were infected with rubella while pregnant terminated their pregnancies due to the serious risks from CRS.
Following one such abortion, the fetus was sent to Plotkin at the laboratory he had devoted to rubella research. Testing the kidney of the fetus, Plotkin found and isolated the rubella virus. Separately, Leonard Hayflick (also working at the Wistar Institute at that time) developed a cell strain using lung cells from an aborted fetus. Many viruses, including rubella, grew well in the resulting cell strain, and it proved to be free of contaminants. The strain was eventually called WI-38.
Plotkin grew the rubella virus he had isolated in WI-38 cells kept at 86įF (30įC), so that it eventually grew very poorly at normal body temperature. (He chose the low temperature approach following previous experiences with attenuating poliovirus.) After the virus had been grown through the cells 25 times at the lower temperature, it was no longer able to replicate enough to cause illness in a living person, but was still able to provoke a protective immune response. This rubella vaccine is still used in the United States today as part of the combined MMR (measles, mumps, and rubella) vaccine.
Ethical Issues with Human Cell Cultures
Although it has now been used in the United States for more than 30 years, Plotkinís rubella vaccine was initially ignored in the U.S. in favor of vaccines developed using duck embryo cells and dog kidney cells. In the late 1960s, there was concern in the country that a vaccine developed using a human cell line could be contaminated with other pathogens, though this concern did not seem to have any documented evidence behind it. This is somewhat interesting in light of the discovery earlier in the decade that polio vaccines developed using animal cells were contaminated with a simian virus, which was one of the reasons researchers began using human cell lines in the first place.
Plotkinís vaccine was first licensed in Europe in 1970 and was widely used there with a strong safety profile and high efficacy. In light of that data, and of larger side effect profiles with the other two rubella vaccines, it was licensed in the United States in 1979 and replaced the rubella vaccine component that had been previously been used for Merckís MMR (measles, mumps, rubella) combination vaccine. Plotkinís vaccine has been used in the country ever since. In 2005 the CDC declared rubella eliminated from the United States, though the threat from imported cases remains.
Groups that object to abortion have raised ethical questions about Plotkinís rubella vaccine (and other vaccines developed with similar human cell strains) over the years.
Because of its position on abortion, members of the Catholic Church have asked for its moral guidance on the use of vaccines developed using cell lines started with fetal cells. This includes the vaccine against rubella as well as those against chickenpox and hepatitis A, and some of the rabies and mumps vaccines. The official position according to the National Catholic Bioethics Center is that individuals should, when possible, use vaccines not developed with the use of these cell strains. However, in the case where the only vaccine available against a particular disease was developed using this approach, the NCBC notes:
One is morally free to use the vaccine regardless of its historical association with abortion. The reason is that the risk to public health, if one chooses not to vaccinate, outweighs the legitimate concern about the origins of the vaccine. This is especially important for parents, who have a moral obligation to protect the life and health of their children and those around them.
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