Is it Morally Permissible to Use the Covid-19 Vaccine?

December 04, 2020
Saint Louis soignant les pestiférés, Louis Testelin l’Aîné

As several manufacturers announce the imminent development of a vaccine against Covid-19, many rumors circulate about those vaccines that suggest a moral impossibility to use them.

The pharmaceutical situation is extremely complex and evolving. To date, there are no less than 32 different vaccines under development, using 4 distinct production methods.

The present article is concerned exclusively with the answer to this moral question: on the concrete basis of how a vaccine works and how it is prepared, may such vaccine be used without committing a sin?

Everyone is free to have their opinion on the origin of Covid-19, on the way in which it has been managed in various places, on the vaccination policy of a particular country, on vaccination in general; but all these elements do not alter the moral conclusion given here.

This article has three parts, each necessary to understand the moral judgment made.

Saint Sébastien soigné par sainte Irène, Georges de La Tour


The Vaccine Idea

The idea of preparing the body against the harmful effects of poisons or infectious agents is not new. It could date back to king Mithridates (132 - 63 BC), who was said to have taken small amounts of different poisons in order to get used to them. This idea can be found today in desensitization, which aims to reduce inappropriate reactions in allergic subjects. The subject is brought into contact with increasing amounts of the elements to which he is sensitive, in order to ultimately suppress the allergic reaction to these elements.

In vaccination, the mechanism is different. It involves administering all or part of an infectious agent, sometimes only its products, to cause the body to react and allow it to acquire immunity against this agent.

A first important conclusion must be drawn. Vaccination is only using a property of the human or animal body: the so-called “immune capacity” of the body to actively oppose foreign agents that attack it. Thus, if a subject is infected with Koch's bacillus, the agent of tuberculosis, and recovers, he will be immune to a new infection: this is natural immunity. If another subject is vaccinated with BCG (Bacillus Calmette-Guérin), which comes from a Koch bacillus rendered harmless, he also develops immunity, produced by vaccination: it is an induced immunity, effective against the Koch bacillus.

But it is obvious that this induced immunity is also natural: the only difference is in the way in which it is produced. This induced immunity is often less lasting because the required reaction is less significant than during an illness.

The Various Types of Vaccines

Until now, vaccines could be classified into two categories: live attenuated vaccines and inactivated vaccines.

In the first case, before being administered, the infectious agent is modified in order to render it harmless, but while retaining its antigenic power, that is to say its ability to provoke an immune reaction. The case of BCG is characteristic of this method. The immune system attacks the vaccine agent and will remember its response: it will then be able to defend itself against a future attack from the infectious agent.

However, this type of vaccination is contraindicated for immune-compromised subjects – those whose immune system is deficient – because then there is risk of a true infection. It happened with the smallpox vaccination, causing many tragedies.

In the case of inactivated vaccines, the infectious agent is dead; it can be administered whole or in part. Among this sort of vaccines, the tetanus vaccine is a particular case: it does not use the infectious agent, but the toxin it produces, which is dangerous and even fatal. This toxin is detoxified before it is administered so that it is no longer dangerous, but retains its antigenic power.

Inactivated vaccines can be associated with so-called “protein” vaccines: the vaccine agent is composed only of proteins from the envelope of the virus, or of its entire envelope emptied of its contents.

Another variant consists in using a virus that is harmless to humans, in order to introduce the vaccine agent into its cell target (viral vector).

Synthetic Vaccines

A new type of vaccine has been studied for the last ten years. It was first considered for diseases such as Ebola or Zika. The idea was picked up for the Covid-19 vaccine.

Like all living things, the Covid-19 virus contains genetic material formed from ribonucleic acid (RNA). In living things, RNA can exist in various forms: mRNA (messenger) which transmits information from the DNA of the cell nucleus to the systems that will use them; TRNA (transfer), which provides the elements to be assembled according to the mRNA code; RRNA (ribosomal) which constitutes the ribosomes, which synthetize proteins.

The idea of the synthetic vaccine is to copy a small part of the virus, in the form of mRNA. The part chosen in the case of Covid-19 is the part that encodes the spicule, an element that allows the virus to enter into the cells.

This mRNA is administered by vaccine to the subject and enters a cell, resulting in the mRNA multiplication. When it leaves the cell, it is identified as a foreign element and destroyed by the immune system. As a result, the subject acquires an induced immunity which will allow him to fight against a real infection by Covid-19.

The advantage of this method is the speed of its development. In fact, the two laboratories which have already announced very satisfactory results use this method. The Russian laboratory Gamaleya produces a vaccine in a similar fashion, but uses a "vector," that is, a virus harmless to humans, to introduce the RNA fragment. This could pose a moral problem which will be examined later.

Preparing Vaccines

There are three stages to preparing a vaccine: design, production, and laboratory testing. During these three stages of development, a moral difficulty may arise due to the environment in which the vaccine is prepared.

It should be noted immediately that vaccines against diseases transmitted by bacteria are not included in this discussion. Indeed, in this case, the culture medium is only a set of nutrients that the bacteria use for food: glucose, water, calcium, etc.

In the case of viral vaccines, the difficulty is that each of the three stages of their preparation may require a virus culture, requiring an environment composed of living cells. In the particular case of synthetic vaccines, this is only for the testing phase.

However, virologists use three types of cells: (1) cells derived from human or animal organs, (2) continuous lines1 which are often of a cancerous origin and can multiply almost indefinitely, and (3) human embryonic cells, which also multiply for a very long time.

Human Embryonic Lines

Among the latter, there are currently at least three lines that originated from an abortion: the HEK-293 line, from a fetus aborted in 1972 in the Netherlands; the MRC-5 line, from a fetus aborted in 1966 in England, and the line Per.C6, from an aborted fetus in the Netherlands in 1985.

The use of cells from aborted fetuses to produce vaccines has therefore been going on since the 1960s, and has already led to the development of various vaccines, such as those that prevent rubella, chickenpox, hepatitis A and shingles.

In the development of vaccines against Covid-19, these cells are used to produce either viral vectors (adenovirus), which will transport the vaccine agent, or the protein of the coronavirus spicule, which will elicit an immune response.

Unfortunately, pharmaceutical laboratories prefer to use cells obtained from fetuses rather than adult cells, which age faster and stop dividing. Fetal cells are also less likely to be infected with viruses or bacteria, or to have undergone genetic mutations.

Saint Sébastien soigné par sainte Irène, Georges de La Tour


The question is whether one can – or, in some cases, must – use a vaccine that has been grown on cells obtained from abortion.

The crime of abortion is so abominable and so prevalent today that at first glance this question may seem unnecessary; spontaneously, the Catholic answers: no.

In reality, the problem may turn out to be extremely delicate, for it happens that in certain very particular circumstances one can be confronted with duties so serious that it could lead to a real moral dilemma. In such daunting cases of conscience, the support of moral theology is essential to examine the situation in depth, in order to discern the good to be accomplished.

Preliminary Remarks

It is necessary to note that there are no fetal cells injected when the vaccine is received, as some believe: they are used only for the culture of the viruses, and are moreover destroyed by the viruses, as are the infected cells in a patient. But this does not change the moral problem.

It should also be noted that it is not the use of the fetal cells themselves that is to blame, because they could have been obtained lawfully: in the event of spontaneous abortion or miscarriage. It is the fact that they were obtained by an evil act, an abortion.

Distinctions to be Made

The principle that guides our reflection in this situation is that of cooperation in evil. The general question is: is it permissible to cooperate in the evil or the sin of others? Moral theology has given the necessary explanations.

Helping a sinner to commit his sin is called "cooperation in evil," regardless of the kind of help given. For such cooperation to exist, the action of the cooperator must have a real influence on the evil act, through the help given to produce it.

To be able to judge, the cooperation must be properly analyzed. This is crucial. Those who neglect these details may not judge properly the morality of cooperation.

Cooperation is said to be immediate when the cooperator performs the sinful act together with the sinner, for example if he helps the thief to take away the booty and hide it. This is also the case of the surgical assistant that performs parts of an abortion together with the abortionist.

Cooperation is said to be mediate when the cooperator provides what will help the sinner – material, necessary action, means – to commit the sin or which will allow him to do it more easily. Such is he who holds the ladder for the thief, or the nurse who assists the abortionist.

This mediate cooperation, finally, can be more or less “close” or “remote,” according to whether the help given has more or less influence on the sin committed, or has a more or less close connection with it. So, to sell an idol to a pagan so that he can worship it is close cooperation. But selling the wood from which an idol will be made is a matter of remote cooperation.

Moreover, depending on the intention, we distinguish a formal cooperation, when the cooperator voluntarily consents to the sin in which he is involved. Thus, whoever helps a burglar by keeping watch, for example, while approving of this sin, formally cooperates in the theft. Civil law will also call him an "accomplice."

Cooperation is material when the cooperator does not want to sin, but acts while foreseeing that the sinner will abuse the help offered in order to commit the sin. Thus, the bar owner who, only for the money, agrees to provide a few drinks to an already tipsy customer, participates in the sin of drunkenness but does not formally cooperate with the intentions of the drunkard.


Formal cooperation is always illicit and forbidden, because the agent takes upon himself the sin with which he cooperates. The cooperator himself intends the sin.

Immediate cooperation, even only material, is illicit, because it is an evil deed, and most of the time a sin identical to that of the principal sinner. For example, a surgeon's assistant who participates in sterilization – tubal ligation or vasectomy – commits the same sin as the surgeon. For his action directly influences the sinful act which could not be committed without him or at least with much more difficulty.

Mediate cooperation may be licit or illicit. Most of the time and usually, it is illicit, because one should always seek to avoid evil actions or to avoid cooperating with them.

However, for a real utility or a serious necessity, one can sometimes be required to perform an act which, although good in itself, will be a mediate cooperation with a bad action.

The usefulness or necessity in question can be so compelling that one is then excused from the obligation to avoid cooperation in evil. In this case, it is said that there is a “proportionately grave reason” for cooperating licitly.2

Let’s take a general example, by considering the various possible agents around an abortion:
- Immediate cooperator: the surgeon's assistant who performs part of the abortion.
- Close mediate cooperator: the assistant who helps the doctor by passing him the instruments.
- Less close mediate cooperator: the nurse who prepares the woman for the operation.
- Even less close mediate cooperator: he who maintains the operating room.
- Moving further away: he who sterilizes the necessary instruments.
- Remote cooperator: the laboratory that supplies the anesthetic products and dilators, or the manufacturer of the surgical instruments. In both cases, the material provided could be used for operations other than an abortion.
- Very remote cooperator: the company delivering these products.

For every stage of the material cooperation, the “proximity” in relation to the sin committed is very variable. Are we to say that each and every one of these material cooperators is absolutely required to abstain from cooperating? No matter the cost?

Moral theology answers: No. The influence of the cooperation on the evil deed is so weak – for example, for the orderly who cleans the operating room – that a reason such as keeping one's job is enough to continue doing it.

On the other hand, the stronger the influence exerted, the more serious the reason to continue must be. And when the closeness is too great, no reason can excuse. One must refuse, even if it means finding another job.

Application to Vaccines Prepared With Cells Obtained From Abortion

It is now a question of analyzing the cooperation of those involved in the preparation or use of a vaccine prepared with cells obtained from an abortion. We only speak here of material cooperation, because formal cooperation is always illicit.

Whoever makes or markets this vaccine is cooperating with the sin of abortion in a way that, although it cannot be called close, can be viewed as immoral. Culpability varies, however, depending on the role played.

Whoever runs a pharmaceutical company profiting from a past abortion bears a greater responsibility. First, because he could have chosen not to make this vaccine; second, because he should stop using the cell lines in question and choose other lines that do not pose a moral problem, even if this has its drawbacks.

The researcher who chooses which cell lines to work on finds himself in a similar situation: he is profiting from a past crime.

But the lab technician who is just one executor, or the truck driver delivering the vaccine, have only distant cooperation, so it is acceptable, especially for the second.

The doctor who vaccinates a patient, or the patient who is vaccinated, has only distant cooperation, for these acts only encourage and promote the sin of abortion in a very remote and very slight way. For sufficient health reasons, such acts could therefore be morally permitted.

A young woman who is to get married can thus receive the rubella vaccine, although such a vaccine is almost always prepared on fetal cells obtained by abortion. The reason is the danger for the child: if a woman contracts rubella during pregnancy, especially during the first trimester, the risk of birth defects – eye, hearing or heart – are significant. These malformations are permanent.

However, if there exists a vaccine derived from cells not obtained from an abortion, and it is available, it is the one that must be used.

Saint Sébastien soigné par sainte Irène, Nicolas Régnier


Here we are only interested in the moral aspect of the use of an anti-Covid vaccine, in reference to its preparation or manufacture.

Lines Used as Part of the Vaccine against Covid-19

The complete list of vaccines in preparation is given in the document annexed to this article. This document specifies the responsible company and the eventual use of cells from an aborted fetus in any of the phases of the preparation: design, production and testing.

List of vaccines currently in preparation:

Moral Judgment according to the Principles Laid Down

Since some of the proposed vaccines were not prepared illicitly, they do not pose a moral problem for use from this point of view. They should therefore be preferred over others.

Those that have used a morally illicit preparation should be avoided as much as possible.

But what if, in a particular case, a person finds it necessary to be vaccinated and is unable to obtain a "licit" vaccine, having only an "illicit" vaccine available? This may occur for health reasons (vulnerable elderly person), or because of the professional situation (exposed medical personnel) or for professional reasons, such as traveling by plane. There is already at least one airline – Qantas in this case – which has warned that, as soon as vaccines are available, it will require vaccination to accept a passenger. It is very likely that this requirement will be quickly taken up by many airlines.

As cooperation is only distant, and the reason given is serious enough, it is possible in these cases to use such a vaccine. Moreover, it remains for each individual to judge, with the help of appropriate advice, this real need.

It must be clearly stated that we are here in the domain of a prudent judgment, which cannot be uniform for all and in all cases. Moral theology says what is lawful or unlawful. It gives the principles. But it is for personal prudence to judge their application on a case-by-case basis.

As for the considerations outside this question of the licitude according to the source and preparation of the vaccine, they are on the order of personal opinions. Like any opinions which cannot be absolutely proven, it is vain and impossible to want to impose them on everyone.

Everyone is free to have their opinion on the origin of Covid-19, on the way in which it has been managed in various places, on the vaccination policy of a particular country, on vaccination in general; but all these elements do not change the moral conclusion given here.

One last remark

It should be noted that, in addition to the case of these vaccinations that we have studied, cooperation with evil occurs in many analogous situations: the latter can be treated and resolved according to the same moral principles. Thus:

Should we stop paying taxes because part of the money is used to reimburse abortion or assisted reproduction?

Should we agree to get supplies from a pharmacist who sells illicit products: abortifacients, condoms, contraceptives? Wouldn't that be a form of encouragement?

Should we accept treatment from a doctor who approves of abortion and prescribes the pill?

Should we agree to go to a department store or a bookstore that sells bad magazines?

Should a cashier refuse to collect payment from a customer who is buying a bad DVD?

It is clear that the list could go on and on.

A final example will be taken from the New Testament: Is it licit to eat the idolothytes, that is, meat sacrificed to idols (1 Cor 8: 1)?

To properly situate this question, it is important to know that all the meat consumed in Antiquity necessarily passed through the temples. Moreover, there is only one word in Greek, mageiros (used exclusively in the masculine), to designate the priest, the butcher and the cook: for those who wanted to abstain from immolated meat, there was no other meat to eat.

Let us add that the sin of idolatry is one of the most serious, since it attacks God himself.

St. Paul answers that it is permissible to eat these meats, unless it scandalizes the neighbor. This means that whoever consumes this meat is not participating in the sin of idolatry. Otherwise, St. Paul could not have answered thus.

Likewise, anyone who is in a situation of sufficiently distant material cooperation in the use of a vaccine against Covid-19, the manufacture of which would have benefited from one of the above-mentioned cell lines, does not participate in the sin of abortion committed 35, 48 or 54 years ago.

However, as has been said, one should, as far as possible, avoid cooperation in evil, even material, and if there is a choice, take the vaccine which poses no moral problem.

However, we must not be content with this deplorable state of affairs and do nothing. Influential Catholics must use all their power to influence the pharmaceutical industry to develop their new vaccines on cellular carriers that do not pose any moral difficulty.

Father Arnaud Sélégny +

  • 1. A cell line or cellular line is a homogeneous population of cells, stable after successive mitoses (divisions), and theoretically having an unlimited capacity for division.
  • 2. Merkelbach, Summa theologiae moralis, t. I, Paris, Desclée De Brouwer, 1931, pp. 394-400
Saint Sébastien soigné par sainte Irène, Dirck van Baburen