The Morality of Vaccines Made Using Embryonic Cell Lines

Photo Credit: James Gathany Content Providers(s): CDC [Public domain], via Wikimedia Commons
Vaccines certainly cause a lot of public tension. I’m not just talking about those who disagree that vaccines are safe and effective; how some vaccines are made can raise some understandable moral concerns.

To make some vaccines, like the Rubella vaccine for example, we need to use diploid[1] human cells from human embryos. In this post I’d like to explore a few questions about this: Why do we need those cells? Where do those cells come from? And what moral questions do these cells raise for Christians?

What Do Human Embryonic Diploid Cells Have To Do With Vaccines?

I think most people are familiar with the general idea of vaccines: they contain a part of a virus that your immune system can recognize and remember, but that won’t infect you like a normal version of the virus. If you get infected with the full-strength virus later then your body already knows how to fight it because it looks similar to the vaccine.

So the question is, how do we get those parts of viruses to make vaccines with?

The bottom line is that we need to grow a lot of viruses. And viruses don’t grow by themselves – they need cells to infect and be built in. We need lots of virus in order to make lots of vaccine, so we need lots of cells too.

In some cases like the measles or flu vaccines we can use the cells in developing chicken eggs to grow viruses. Unfortunately that doesn’t always work because viruses can be highly specific about the types of cells they can infect. Sometimes you need to use human cells, but of course we don’t want to infect humans.

Cartoon of how viruses like Rubella leave a cell through the cell membrane. Once it’s out, we can collect and use them to make vaccines. Animation by Gleiberg at German Wikipedia [CC BY-SA 2.0 de (, via Wikimedia Commons
Ideally we can just grow human cells in a lab, infect them with a virus, and collect the viruses when they pop out of the cells. But those cells would need a few abilities to be useful to us:

  1. They need the ability to be infected by the virus. Different viruses infect different types of cells in the body.
  2. We need to be able to grow lots of these cells. Human cells that aren’t cancer get old after a while and stop making more cells. This is called The Hayflick Limit and it’s bad news for for mass production.
  3. They need to stay unchanged enough that we can use them reliably. Some cancer cells may satisfy the other two criteria, but cancer is highly unstable, and dangerous if the cells somehow got into a vaccine.

Here’s where the human embryonic diploid cells come in.

Embryonic cells are so young that they can divide enough times to be useful for mass production. Just two samples of embryonic cells (cell lines) called WI-38[2] and MRC-5 have been grown for making vaccines since the 1960’s without us needing to collect any new cell samples.

Certain types of embryonic cells like WI-38 can be successfully infected with viruses we need vaccines for like Rubella.

Since embryonic cells are also normal healthy cells they are also genetically stable. That along with their long dividing life makes embryonic cells uniquely ideal for industrial production of vaccines.

So that’s all pretty great until we get to the part where the cells need to come from an embryonic human who also needs the cells.

What Moral Questions Should We Ask About Using These Cells?

In a sense it’s not hard to see why some people have concerns about vaccines cultured in human embryonic cells. The only way we have to do that is to get them from a deceased human.

Both WI-38 and MRC-5 cell lines were samples taken from fetuses aborted in voluntary abortions in the 1960’s. That makes for instant moral tension for Christian people who are morally opposed to voluntary abortions.

But vague tension isn’t helpful. We need to ask how to thoroughly understand and deal with this tension.

I appreciate the Roman Catholic church for usually being pretty methodical about trying to navigate scientific and moral issues, and in this case they do not disappoint. The Pontifical Academy For Life issued a thoughtful response letter to address this specific issue back in 2005, and you can read the whole thing here.

The basic idea the letter outlines is that by using cell lines produced from abortions, and by not publicly standing against the act of abortion that made the cells available, researchers producing and people using the vaccines bear some moral “cooperation” with the abortions.

The letter is short, carefully worded, and I think those issues are well explained, so I do recommend reading it for yourself. I think I have a criticism of it, but mostly agree with the practical conclusions.

My criticism is that the entire letter hinges on the moral problem being described as “cooperation” with an abortion. Personally I think that is a bit of a stretch. There is no evidence that the development of cell lines from these tissue samples had anything to do with the decision of these two women to get abortions, or with the act of the abortions themselves.

As far as I can see, the entire abortion side of this could be seen as a moral compartment that is only relevant to itself. I may disagree with abortion morally, but not disagree with taking cell samples from a human body. If taking the sample doesn’t affect whether or not the abortion occurs, or how it occurs, why should these two things be considered morally connected?

Consider if the samples had been taken from spontaneous miscarriages rather than voluntarily aborted fetuses. Would we say that using the cell lines is cooperation with a miscarriage? I don’t think so.

As for practical conclusions, I think my own view and the Pontifical Academy For Life letter mostly agree. Vaccines that use embryonic human diploid cells have done and continue to do a great deal to decrease suffering and death due to disease in the world. If the cell lines issue bothers your conscience, and there is a different vaccine available, using the different vaccine would be a great option.

If there is no other option, then using the vaccine is a moral option regardless. At worst, it’s a great moral good to protect yourself and others with only a weak distant connection to something many Christians consider immoral.

And if someday we develop the technology to culture viruses in cells that have a morally unquestionable origin for all Christians, then that’s all the better. But in the meantime we have these cells already, and any weak connection to abortion they have is half a century behind them.


[1] Diploid means cells that have two sets of chromosomes, like most (but not all) cells in the human body.

[2] Leonard Hayflick was also the fellow who worked to establish the WI-38 cell line. Establishing cell lines involves more moral question than just abortion. Nature has a good introduction to that interesting story here:


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