COVID Vaccines and Fetal Cells

Is there a pro-life conflict over vaccination?

HeLa human fibroblast cells, image created by Tom Deerinck, NIGMS, NIH. Source: National Cancer Institute, public domain

By Amy Rogers, MD, PhD

With the good news coming from phase 3 clinical trials, vaccines are on many people’s minds this week. Part of the conversation is about acceptance when a COVID vaccine becomes available.

Vaccine hesitancy, or outright vaccine refusal, has been a thing since long before COVID. In fact it dates back to the very first vaccinations against smallpox in the 18 thcentury, and it spans cultures worldwide for reasons that are often contradictory yet specifically relevant to a particular time and place. (If you’re interested in understanding the complex social and psychological factors at play, I highly recommend reading On Immunity by Eula Biss.)

Reasons for vaccine hesitancy vary, but apparently one reason is being discussed widely right now. In the past few days, two people have independently asked me about a moral issue around vaccination: are vaccines made from, or do they contain, aborted human fetal cells?

Let’s talk about that.

To understand the answer to this question, you must first know something about how a virus reproduces, and what a vaccine is.

The Birds and the Bees of Viruses

In this blog post back in April, I explained how viruses reproduce, and why this unusual, semi-alive existence makes it very hard to develop drugs that can treat viral infections. Bacteria, on the other hand, offer lots of good drug targets, and therefore we have become accustomed to having a choice of antibiotics to treat bacterial infections. (That situation is not likely to last forever, unless we get more serious about funding research on new classes of antibiotics.)

To summarize a lot of biology, viruses are so small and so simple that they lack the basic equipment needed to make more of themselves. In order to reproduce, a virus must enter (infect) a living cell, and then hijack the machinery of that cell to manufacture new viruses. In essence, viruses don’t breed. They’re made in a factory.

Why a Vaccine?

To immunize means to train one’s immune system to recognize a disease-causing germ as something that is harmful and must be destroyed. Your body isn’t born knowing (for example) that the measles virus is bad. It learns, after exposure. Having learned, in future encounters, your immune system is faster and more effective at banishing the invader. The result? You only get the disease once, no matter how many times the virus attacks.

This type of natural immunity can be very effective and long-lasting (though not always). So why mess with a good thing? Why use an artificial vaccine to train the immune system, instead of letting natural exposure do the job?

Because natural immunity comes with the risk of getting sick, becoming disabled, or dying.

Public health experts don’t push vaccines because artificially acquired immunity is better than naturally acquired immunity (although in some cases it is). They push vaccines as the best route to immunity because it’s safer.

This is based on the premise that in order to get FDA approval for any given vaccine, the disease it prevents has the potential to cause significant harm AND the vaccine has been adequately tested to be overwhelmingly safe. It’s a balance between risk and reward, one that can shift depending on how deadly the infection is (see my yet-to-be-written post on the Sabin polio vaccine).

What’s in a vaccine?

A vaccine must contain something that comes from the virus you’re vaccinating against. That “something” can be the entire virus, or certain body parts from it.

Humans have been making vaccines for over two hundred years. For most of that time, vaccines contained the whole virus, either as a dead body or in weakened condition.

So how does a vaccine manufacturer get a bunch of dead or weakened viruses? They have to grow them first.

With bacteria, this is much easier. Bacteria are fully alive, single-celled organisms. If you feed them, they will multiply. A vaccine manufacturer can grow disease-causing bacteria in tanks of nutrient broth, and then deactivate them for use in a vaccine.

As I just explained, however, viruses don’t reproduce on their own. You can’t just give them food and shelter. They need hosts. So to produce a bunch of viruses for use in a vaccine, manufacturers have to first grow a bunch of cells that the virus can infect.

What kind of cells?

Viruses are extremely particular about their hosts. In fact, some viruses will only infect one cell type in one particular species. Some viruses are a little less specific, and can infect multiple cell types from several different species-but never too far away on the evolutionary tree. You know this from common experience. Do you worry about catching a deadly virus from a potato plant? No, even though potato plants suffer from deadly viral infections. Do you worry about catching a deadly virus from other mammals, like bats? You should, because some viruses can infect both bats and humans.

As a general rule, any virus that causes serious disease in humans will only grow in cells from vertebrates (animals with a backbone). For example, you can’t grow chickenpox virus in plant cells or worm cells. Which would make vaccine production easier, but it would also mean you could catch chickenpox from your salad. Yuck.

Most viral vaccines are manufactured using cells that most people don’t care about. A good example is the annual flu (influenza) vaccine. The viruses that cause flu in humans can also infect birds and pigs. So fertilized chicken eggs have long been used as factories to manufacture the flu vaccine. The cells of the chick embryo inside the egg are infected by the virus, and produce more of it. After a suitable period of growth, flu viruses are purified from the eggs, and then killed. The dead bodies of the flu virus are what go into the vaccine. Because the virus is dead, it cannot give you the flu. It’s possible for a tiny amount of material from the egg or chick to end up in the vaccine. That’s why before getting a flu shot, they ask you if you have an allergy to eggs.

Most people think it’s ethical to eat eggs, so most people have no moral qualms about the flu vaccine.

Cell lines and abortions

Embryonic chickens (eggs) are useful for growing influenza virus, but they won’t work for all viruses. Most vaccines are manufactured using mammalian cell lines. A cell line is like a sourdough starter. It’s cells propagated from a unique origin, from a particular animal and a particular organ or tissue. With proper care and feeding, cell lines will multiply in a laboratory. They can be infected with a virus and used to generate a batch of virus for vaccine production.

Animal cell lines can sometimes be used. For example, polio vaccines are made using cells descended from the kidney of an African green monkey derived in 1962 (Vero cells). The three original ( 1969) rubella vaccines were made in duck, dog, and rabbit cell lines.

For some viral vaccines, human cell lines are used. In the case of present-day vaccines against chickenpox (varicella), rubella (the “R” of MMR), and hepatitis A, production uses fetal cell lines that were created from the tissue of two or three babies who were aborted in the 1960s. The cells in use today are descendants of those cells from the children, not the cells themselves. The cells are used to manufacture virus. Then the virus is purified away from the cells and turned into a vaccine. There are no actual fetal cells in the cell lines anymore, or in the vaccines. For what it’s worth, the elective abortions had no connection with the subsequent research. If you’re interested in details of the history, visit my sources ( source 1, 2, 3) or read The Vaccine Race by Meredith Wadman.

The Catholic Church and vaccines

First, let me emphasize that the Roman Catholic Church is very supportive of vaccination in general. (See: Pontifical Academy for Life statement from 2017)

However, the association between a couple of widely used vaccines and abortion creates a dilemma for those who hold strong pro-life beliefs. It is far beyond the scope of this essay to explore the ethical angles of this decision. However, the Roman Catholic Church has deliberated these issues, and consulted experts, and in 2005 made a statement on the matter. The Congregation of the Doctrine of Faith issued a thorough reply to the question of a Catholic’s moral obligations in regard to using vaccines that are prepared using cell lines derived from aborted human fetuses. At the time, the Congregation was headed by Cardinal Joseph Ratzinger, who later became Pope Benedict I. You can explore the whole document here, and more here, but here are the takeaways:

“As regards the diseases against which there are no alternative vaccines which are available and ethically acceptable, it is right to abstain from using these vaccines if it can be done without causing children, and indirectly the population as a whole, to undergo significant risks to their health. However, if the latter are exposed to considerable dangers to their health, vaccines with moral problems pertaining to them may also be used on a temporary basis.

“As regards the vaccines without an alternative, the need to contest so that others may be prepared must be reaffirmed, as should be the lawfulness of using the former in the meantime insomuch as is necessary in order to avoid a serious risk not only for one’s own children but also, and perhaps more specifically, for the health conditions of the population as a whole — especially for pregnant women.”

In other words, the official Catholic position is that it is acceptable for a person to use these vaccines if there is no alternative vaccine made without the moral taint; and that Catholics should press for the availability of alternatives. Such alternatives may exist but not be in the marketplace (see: rubella: human cell version introduced in 1979, and older versions discontinued). Or no alternative may exist. Or patients might have a choice:

“For adults, the GSK company makes an ethical shingles vaccine called Shingrix. Merck’s vaccine against shingles, Zostavax, is derived from aborted fetal cells.” ( Source)

What about the new vaccines against COVID-19?

The SARS-CoV-2 pandemic has pushed forward a host of brand-new vaccine technologies. I’ll save the science details for another post. In the context of pro-life ethics, the new vaccines fall into three categories:

  1. Vaccines that are manufactured using abortion-tainted fetal cell lines
  2. Vaccines that are manufactured using other cell lines
  3. Vaccines that do not require cells at all

For a comprehensive list of each, consult sources: 1; 2

The exciting news is that the two vaccines that are closest to approval are in the third category. Pfizer/BioNTech and Moderna both released early data in the past 10 days showing greater than 90% efficacy in preventing symptomatic COVID. Both of these vaccines are made using an information-carrying molecule called RNA. There is no virus of any kind in the vaccine, so the companies do not need cell factories to make it.

Key points:

  • Old-school vaccine technology uses cells to manufacture viruses
  • For many vaccines, the cells are from non-human animals
  • For some vaccines, the cells used to manufacture the viruses are descendants of cells derived from babies aborted fifty or more years ago
  • Vaccines may contain trace amounts of the cells from which they were purified
  • No vaccines contain aborted human cells
  • The Roman Catholic Church supports vaccination in general, and allows the faithful to use abortion-tainted vaccines if no alternative exists
  • Some COVID-19 vaccines in development use the controversial cell lines
  • Some COVID-19 vaccines in development use revolutionary new technology that doesn’t require any cells at all

Questions? Ask me.

Amy Rogers, MD, PhD, is a Harvard-educated scientist, novelist, journalist, and educator.

Author may receive benefits from links to amazon book products.

Originally published at on November 17, 2020.

Amy Rogers, MD, PhD, is a Harvard-educated scientist, novelist, journalist, and educator. She blogs about coronavirus at

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