Vaccines produced in cell strains derived from human embryonic tissue

March 2003

---Philip A. Brunell, MD

Those of you who do not read the letters we publish may be missing the best part of Infectious Diseases in Children. Last month a letter was published concerning a parent’s need to know that certain vaccines their children were to receive were prepared in cell strains which had been derived from human embryonic cells about 40 years previously. The respondent felt that some parents might object to the receipt of these vaccines by their children on religious grounds. The letter raises some interesting questions. What is the obligation to routinely inform parents about the source of vaccines at the time that their children are to be vaccinated? What is the position of clerical authorities regarding the use of these vaccines?

The first point that the reader makes is that we erred in reporting that vaccines are not prepared in human tissues, and he is absolutely correct. Mea culpa. We blew it! When I checked the copy, which stated, “The varicella vaccine (Varivax, Merck) was produced from diploid cells that originated from tissue extracted from aborted calves in 1966, and vaccines against rabies, mumps, rubella, hepatitis A and smallpox vaccines were also developed using aborted animal tissue,” — and that aborted human fetal tissue has never been used in vaccine development, I marked up the galleys to indicate that this was incorrect. The editorial staff, checking on me, as they should, “confirmed” this incorrect information and published it as is. Thus, one of our alert readers brought this error to our attention. Having worked with varicella virus in human embryonic cells myself for more than 40 years, there is no way I could have not been aware of the use of these cells for vaccine production. Several other vaccines are prepared in cells derived from human embryonic cells, too.

About 40 years ago, cells from human embryos were grown in tissue culture. It was learned at that time that a single embryo could provide almost a limitless supply of cells, which remained essentially unchanged if passaged about 40 times. These strains, in contrast to the malignant cell lines that were existent at the time, retained their normal chromosome number and did not produce tumors. It was soon found, moreover, that they would support the growth of many viruses. Varicella virus and hepatitis A viruses were propagated in these cells, whereas it was difficult if not impossible to grow them in other types of cells. They provided an almost ideal substrate for the production of some of the vaccines we now use. Before the discovery of these cells, some vaccines were grown in avian eggs or cells derived from avian embryos. Other vaccines (eg, polio) were grown in kidney cells obtained by killing monkeys. In contrast to the human diploid cells, each time cells were required, a monkey had to be killed to obtain their kidney to produce cell cultures. This not only put a drain on the monkey population but also carried the risk of harboring monkey viruses, eg, SV40, which is known to be oncogenic in some species. Also, some of the monkeys bit handlers and infected them with herpes B virus, which was often fatal. At the present time rubella, hepatitis A, rabies and varicella vaccine are grown in cells derived from human embryonic lung cells which were obtained about 40 years ago from one or two aborted embryos, passaged several times and frozen away until they were needed. There are several strains of these cells but most vaccines are produced in MRC5 cells — which were derived in Great Britain from a single human embryo.

The original erroneous report in Infectious Diseases in Children was not an effort to disguise the origin of the cells used in these vaccines but most certainly was a simple mistake. All one need do is read the Physician’s Desk Reference under Varivax, which clearly states in the fifth line of the description that the virus was “introduced into human embryonic lung cultures.” This information exists in the PDR along with lots of other information that is not shared with parents at the time of immunization but is public information and available for all to see. Indeed at the Web site, the CDC has published a statement on the use of human embryonic cells in vaccines.

The value of these vaccines is undeniably indisputable. The irony is the objection to rubella vaccine to prevent death of and damage to human fetuses, because the vaccine virus was recovered from an aborted fetus. For many this fact denies the issue of the immorality of using cells obtained from a human embryo for use in producing these vaccines. I do not adhere to these beliefs but I do respect them. I have tried to understand the arguments for these beliefs, but as a lay person, I do not have the background to be able to follow many of these arguments. I do understand the primacy of the moral argument, which in the judgement of those who abhor the use of embryonic tissue, supersedes any good that may derive from them. The most valuable document I have seen was on the Web site of the U.S Council of Catholic Bishops (USCCB). The first point made is the objection to prospectively obtaining embryonic tissue by abortion for any use. The second deals directly with the issue at hand — the use of tissues from abortions that have already taken place. It is stated that, “The recipient of the vaccine took no part in decisions to base the vaccine on this morally unacceptable source, but is coping with the results of immoral decisions made by others.” This statement by the USCCB sanctions the use of these vaccines — because the child receiving the vaccine “took no part in decisions.” There are many, however, who do not agree with sanctioning the use of these vaccines.

Why then has this become an issue at this time? Clearly because of the proposal to use human embryos as a source of stem cells in research. The two issues are linked together in this statement from the USCCB. They are to consider the use of embryonic cells in vaccines at their next two meetings. Meanwhile, I will present this problem to a bioethics group here in Washington for their consideration.

The real danger is that this argument will be invoked by some who simply do not want to have their children immunized. This would pose a real danger not only to their children but also to those individuals who may have been vaccinated but did not become immune. An epidemic would threaten the health and well being of both. Please continue to write us. Your letters spark discussion, debates and story ideas.