The Food and Drug Administration granted emergency authorization for the use of a COVID-19 vaccine produced by Pfizer and BioNTech on Dec. 11. Other products from Moderna and AstraZeneca are in the pipeline. All of these vaccines relied on a fetal cell line called HEK-293 for testing or production. Is this a reason not to use them?

HEK-293 is a cell line that scientists refer to as "immortal" because it continues to divide and reproduce. It was derived from the kidney cells of an aborted fetus in 1973. Since then, it has propagated through multiple generations and been modified in many ways for specific applications. Today, it is widely used in biology experiments of all kinds.

Seven years ago, we undertook an examination of the morality of using HEK-293 in our own scientific research at Catholic University. These were our conclusions.

Those directly involved in the abortion in 1972 -- the woman who procured it, the doctor who performed it, perhaps the researcher who collected the cells -- were no doubt guilty of serious sin.

Pfizer and Moderna came into the picture long afterward. They didn't cause the abortion. Of course, they are in the business of developing vaccines, so they might cause other abortions by creating a demand for new fetal cell lines.

But that hasn't happened. HEK-293 is unique, and researchers use it (rather than some newer cell line) for two reasons. First, precisely because it is so widely used, it's known to be dependable, so experiments don't go awry. Second, when comparing one vaccine (or whatever else is being tested) against another, it's important to hold everything else constant.

So, Pfizer and Moderna didn't cause the original abortion and haven't created a market for later ones. But using the fruits of HEK-293 might have a bad effect on the people who work there. If their daily work, and maybe their career prospects, benefit from abortion, they might relent in their condemnation of the practice. They might even begin to think there are things to be said on both sides of the question.

This is not a trivial matter. Catholic moral thinking is concerned with the internal effects of our actions -- the kind of people they make us become -- no less than the external effects. The thing is, HEK-293 is so widely used that it is difficult, if not nearly impossible, to do biological research without coming into contact with it in some way.

People would have to forsake careers in medicine and the life sciences if they really wanted to avoid that taint.

What about people like us, ordinary citizens who take the vaccine? We certainly benefit from the role HEK-293 played in the trials and production of vaccines. Some people might be tempted to count that as a credit on the moral balance sheet for abortion. Then, too, there is a danger that taking the vaccine will communicate a bad lesson to others (like our children) about the value of human life.

These are serious risks. But if we refuse to get vaccinated, we could catch and spread to others a potentially fatal disease. We are not required to run that risk to protect our own or our children's purity of heart.

This is how the Congregation for the Doctrine of the Faith put it in 2008: "For example, danger to the health of children could permit parents to use a vaccine which was developed using cell lines of illicit origin."

We are, though, required to make known our objection to the way this all started. And when there are effective alternatives that haven't been developed with the use of fetal cell lines, we should favor them as a way of making our objection known.

- Garvey is president of The Catholic University of America in Washington, D.C.