How “aborted fetal cells” in vaccines contributed to preventing billions of cases of disease and many million deaths [Respectful Insolence]

Massive is the misinformation promulgated by the antivaccine movement, and many are its lies. For example, antivaxers claim that, in some way or other, vaccines cause autism, autoimmune diseases, sudden infant death syndrome (SIDS), cancer, and a wide variety of other conditions and diseases when there is no credible evidence that they do and lots of evidence that they don’t. One of the favorite tropes used by antivaxers to frighten parents out of vaccinating their children is known as the “toxins” gambit, in which antivaxers cite lists of scary-sounding ingredients in vaccines like formaldehyde to claim that vaccines are loaded with “toxins” and that it’s those toxins that are causing all The Bad Things for which they incorrectly blame vaccines. Of course the dose makes the poison and the amounts of these chemicals in vaccines is very small. One example in particular, formaldehyde, is even a normal product of human metabolism and present in the blood at levels far higher than any vaccine. The point is that these “toxins” are, at the doses present in vaccines, not harmful, but the chemical names sure do sound scary.

There is a variant of the “toxins” gambit that is designed to appeal to members of religions that equate abortion with murder, and that’s the claim that there are “aborted fetal cells” in vaccines or, more egregiously (and confusing cultured cells and actual tissue) “aborted fetal tissue” in vaccines. The idea is to paint a picture of vaccine makers grinding up dead fetuses to make their vile concoctions to put in vaccines, no doubt cackling evilly as they do it and demanding more abortions to provide them with their horrific raw materials. (I exaggerate, but only slightly.) The idea of course is to portray vaccines as not only contaminated with something disgusting but the product of evil.

As with most antivaccine tropes, there is a grain of truth distorted beyond recognition here. The virus stocks used to make some vaccines are grown in cell lines like the WI-38 cell line, which is a human diploid fibroblast cell line derived from a three month old fetus aborted therapeutically in the US in 1962. Of course, there’s a huge difference between an immortalized cell line that was derived from a fetus 55 years ago and actual “fetal cells.” While it’s correct to say that WI-38 cells were derived from a fetus, they are hundreds of generations (replications) removed from the original cells from the original fetus. Even though that most anti-abortion of religions, the Catholic Church is not thrilled with vaccines made in WI-38 cells and urges scientists to develop vaccines that don’t use such cell lines, it recognizes the great good vaccines do and concludes that the extreme good of protecting children’s lives from deadly diseases far outweighs the distant evil that created the cell lines. I also note that, in the case of WI-38, the abortion was therapeutic; i.e., medically indicated. It was not elective.

But why is the WI-38 cell line used? And what has been the benefit? However unreasonable antivaxers are otherwise, these questions are not unreasonable. So it was with great interest that I read a study sent to me by a reader (and, as I was going over this one last time early this morning, I saw that my good blog bud Skeptical Raptor also covered this study, albeit from a somewhat different viewpoint), The Role of the WI-38 Cell Strain in Saving Lives and Reducing Morbidity/. It’s open access; so you can read it for yourselves. Basically the authors S. Jay Olshansky and Leonard Hayflick, of the University of Illinois at Chicago and UCSF, respectively, view the development of the WI-38 cell line as a seminal event in the history of vaccines, noting that with the rise of a new antivaccine movement we are poised to take a great step backward in public health:

If the anti-vaccination movement gains any additional traction, developed and developing nations will have taken a dangerous step backward in protecting public health, especially that of children. There are many ways to re-emphasize the health benefits of vaccinations, but one novel approach that represents a perfect example of applied demography in public health is to illustrate how many lives have been saved, and how many people are alive today, as a result of a single breakthrough in the chain of historical events that led to the development and successful dissemination of live attenuated viral vaccines. Here we illustrate how the discovery and use of a single cell strain used to grow most viral vaccines in use today (WI-38 [8] and a later derivative [9]), has already had a powerful impact on human life on an order of magnitude that is unprecedented in the history of public health. This direct application of applied demography will shed new light on (1) the importance of vaccines in saving lives, (2) the chain of fortuitous events that occurred to create a public health breakthrough of this magnitude and, (3) make clear that the anti-vaccination movement represents a serious threat to a proven public health intervention.

They also note that they are only covering one breakthrough and its effects:

We use WI-38 as a point of reference because of its specific link to certain vaccines early in the vaccine movement, and because its development in the early 1960’s served as a catalyst for the field. Full credit for the life-saving effects of vaccines belongs to the breakthroughs, scientific advances, and hard work of countless scientists and health care providers, all of whom together contributed to building the chain of vaccine development and use.

The authors begin with a brief history of vaccines. Before the WI-38 cell line was isolated viral stocks for vaccines like the polio vaccine were grown in cells isolated from monkey kidneys. However it was soon discovered that these monkey cells were often contaminated with simian viruses. The most famous of these is SV-40, which, scientists observed in the early 1960s, could cause tumors in experimental animals. It has never been shown that SV-40 in the vaccines used to make the live virus polio vaccine of in the 1950s and early 1960s has led to an increase in cancer, as I’ve discussed before, but it’s nonetheless a frequent theme among the antivaccine movement that SV40 in those batches of polio vaccine in the late 1950s and early 1960s is responsible for the “cancer epidemic,” or, more risibly, was the source of HIV, the virus responsible for AIDS. Conspiracy theories still abound to this day. In any event, at the time scientists didn’t know that the tumorigenic properties of SV40 observed in animal models at the time didn’t translate to humans, and so the development of SV40-free cells to grow virus stock in rapidly became a high priority. Basically, the development of WI-38 was part of a broader effort to find ways to eliminate SV40 from the polio vaccine.

Contrary to what antivaxers claim, there are a great many advantages to using WI-38 to grow virus stock for vaccines as the authors relate:

The first human cell strain used for the production of licensed human virus vaccines, was WI-38 developed by one of us (L.H.) at the Wistar Institute in Philadelphia in 1962. Unlike primary cell cultures, WI-38 is passaged from one vessel to additional vessels ad seriatim, thus producing almost unlimited numbers of cells from a single source for the manufacture of many human virus vaccines. Because a single cell strain can be frozen for indefinite periods of time, WI-38 has been frozen for 55 years, which is the longest period of time that normal human cells have been frozen. Of great importance, and unlike primary cells, WI-38 was exhaustively tested for safety and efficacy before use [18]. Freezing primary cells for testing is impractical. Since the early 1960’s, the vast majority of human virus vaccines have been grown in WI-38 or its derivatives, making its discovery and continued use a critical innovation in the historical chain of events required for vaccine development [19]. Unlike monkey kidney primary cultures, the importance of WI-38 is that (1) it is derived from a single donor, (2) it is free from contaminating viruses, and (3) it can be frozen for indefinite periods of time and tested for safety and efficacy before use in large scale vaccine manufacture [20]. WI-38 was distributed by Dr. Hayflick gratis to the world’s human virus vaccine manufacturers.

It needs to be acknowledged that one of the authors of the article, Dr. Leonard Hayflick, actually developed WI-38, who wanted to know how many lives had been saved by vaccine derived from WI-38. That being pointed out, on to the study itself. Basically, in order to estimate the number of cases of disease and the number of deaths prevented by vaccines developed using W-38, Olshansky and Hayflick used existing published data on the incidence and number of deaths for each disease in the US in 1960, two years before WI-38 was developed. Assuming that prevalence rates would have remained constant without vaccines, they estimated how many cases of disease and death were prevented in the US and worldwide. They took into account the year of introduction of each vaccine, and analyses carried through 2015 to estimate the effects of the vaccines. Now, I know what you’re thinking. Is it reasonable to assume that the incidence and death rates due to these vaccines would have remained the same without the vaccine? Certainly there’s little reason to assume that the incidence would have changed much, although certainly improvements in medical care might have reduced the death rate independent of the vaccine. There’s also the issue that incidence can vary year-to-year, sometimes (as in the case of polio before the vaccine) dramatically. So we have to view the results of this study as a rough estimate of the number of lives saved. It could overestimate the effect, or it could also underestimate how many lives were saved. It could even do both, underestimating vaccine effect for some diseases and overestimating it from others. Be that as it may, the results are staggering, as the key table from the study shows for the US (click to embiggen):

Overall, the authors estimate that the total number of cases of poliomyelitis, measles, mumps, rubella, varicella, adenovirus, rabies and hepatitis A averted or treated with WI-38-related vaccines between 1960 and 2015 was 198 million in the U.S. and 4.5 billion globally (720 million in Africa; 387 million in Latin America and the Caribbean; 2.7 billion in Asia; and 455 million in Europe). In addition, the estimated total number of deaths averted from these same diseases was approximately 450,000 in the U.S., and 10.3 million globally (1.6 million in Africa; 886 thousand in Latin America and the Caribbean; 6.2 million in Asia; and 1.0 million in Europe). These are incredible numbers, and they are not out of line with other estimates. For instance, data from the Tycho Project indicate that in the US alone, the numbers are likely far higher. Of course, the Tycho Project didn’t restrict itself to just WI-38-associated vaccines; it looked at all vaccines. The point is that the Tycho Project used more rigorous methodology and came up with estimates in the same order of magnitude. Other estimates are also higher than that of Olshansky and Hayflick. The bottom line is that vaccines work. They’ve prevented billions of cases of disease and many millions of deaths. The only reason antivaxers can sound even the least bit plausible when they use the “vaccines didn’t save us” gambit is that, thanks to vaccines, today we aren’t seeing those huge numbers of cases of disease and death.

As self-serving as it might have been, what Hayflick and Olshansky contribute to the data is an estimate of just how important those evil “aborted fetal cells” have been to the overall reduction in disease, suffering, and death due to vaccines. The authors also note how other antiscience trends other than the antivaccine movement would have made the development of the WI-38 cell line difficult or impossible in the US and conclude by noting how many lives are saved by vaccines each and every year. It’s worth citing at length:

Each discovery or breakthrough in the chain of events that led to vaccines becoming a public health success story may have occurred eventually. However, timing is important, and there is no question that when the WI-38 cell strain became available in 1962, it was fortuitously discovered at the same time that the primary monkey kidney cells used to manufacture the poliomyelitis vaccines were found to have been contaminated. Thus, the use of WI-38 represented a catalyst for subsequent vaccine development. In fact, the success of the research that resulted in the development of WI-38 in 1962 occurred when federal research funds were not prohibited for use in studying the biology of tissue derived from aborted human fetuses. However, during several subsequent presidential administrations, that prohibition was enforced. If that prohibition had been in effect in 1962, it is unlikely that in the subsequent 55 years, there would be billions of people who benefitted from virus vaccines produced in WI-38.

A delay of even one year in the development of an uncontaminated cell strain for vaccine development would have cost humanity millions of lives and countless more cases of vaccine preventable morbidity. Today, a majority of the world’s 7.5 billion people have been vaccinated against viral diseases with the use of the WI-38 cell strain and its derivatives. Nearly everyone born in the developed world since 1962 received at least one vaccine manufactured with the WI-38 cell strain, along with a growing proportion of the population in developing nations. WI-38 and its derivatives are still in use for producing many viral vaccines that are distributed worldwide today.

Billions of people are alive today who would otherwise have either died in childhood or who would have been crippled or disabled by vaccine preventable diseases. The World Health Organization estimates that all immunizations now available avert about 2.5 million deaths among children every year, but many more lives could still be saved if vaccines were universally available. In fact, it is ironic that the rubella vaccine (which is produced in the WI-38 cell strain that originated from an aborted human fetus) is vigorously opposed by anti-choice advocates, even though this vaccine prevented over 633,000 miscarriages in the U.S. alone, and countless more across the globe, and it has prevented tens of millions of clinical health issues in children (e.g., encephalitis, autism, deafness, diabetes, etc.) linked to congenital rubella syndrome [27].

Indeed. WI-38 is an excellent example of the sorts of discoveries that ill-advised restrictions on federal funding of research into fetal cells could inadvertently delay and the hypocrisy of some anti-abortion antivaccine activists, who mischaracterize the use of WI-38 cells in vaccine manufacturing as “fetal cells” or “fetal tissue” in vaccines. More recently, perhaps realizing how silly this mischaracterization is, some have started fear mongering about incredibly tiny amounts of “fetal DNA” (i.e., DNA fragments from WI-38 cells that can, if you do really, really sensitive PCR, be detected) as though it were somehow dangerous. The isolation of WI-38 cells is also an excellent example of serendipity in science in that its discovery just so happened to coincide with a time when the safety of the existing vaccines in use was being questioned because of the discovery of SV40 contamination. If not for SV40, vaccine scientists and manufacturers might have had much less incentive to change (or at least to change rapidly) their methods of producing vaccines to using WI-38 cells to grow the viruses used.

So when an antivaxer asks why “aborted fetal cells” are used to make vaccines, point them to this paper. The reasons are simple. Using WI-38 cells to make vaccines against viral diseases facilitated manufacturing huge quantities of much more standardized and safer vaccines that have saved millions and millions of lives and prevented billions of cases of disease over the last 55 years.