Are we obligated to be vaccinated?

by David Copp and Gerald Dworkin

In a survey released at the end of May by the AP and the NORC Center for public affairs research, 49% of Americans said they intended to be vaccinated against the new coronavirus, 31% said they were unsure, and 20% said they would not get the vaccine.

The Supreme Court (Jacobson vs. Massachusetts) has ruled that mandatory vaccination was a legitimate use of State police powers. Justice Harlan wrote “There are manifold restraints to which every person is necessarily subject for the common ground.”

Whether that legal ruling would stand up in the current political situation, and this particular Supreme Court is an open question.

Some more background. We know that vaccination rates for measles and chickenpox have declined in recent years. We know that there is a growing and vigorous anti-vaccination movement in the US.  We know that New York State allowed exemptions for religious or personal reasons and that at least partially as a result, New York had the largest measles outbreak in 25 years. As a result the legislature removed its exemptions, the removal was challenged and the State court dismissed the challenge.

However interesting the legal issues are, in this blog we  are interested in examining the moral or ethical considerations which bear on the issue of whether, if ever, and if so, under what conditions, people are morally required to accept vaccination, even if they object to it. 

We start with the principle that a person is obligated to refrain from causing harm (or significant risk of harm) to others, and obligated to prevent harm to others, when the costs to the person are relatively small and the benefits great, unless the relevant others give their consent.  In saying a person is obligated, we mean that unless the person has a reasonable excuse, or there are additional reasons that outweigh the obligation, the person is blameworthy for his conduct.

There are many possible objections to this principle —we will discuss a few. Some of the objections point to ways that our principle should be qualified, or to exceptions to the principle.  But we believe that in each case the explanation of why there is this qualification or exception does not apply to the case of vaccination. We will elaborate on all this further.

Some might object to the principle by presenting cases where our argument would imply that we are under an obligation but it is clear we are not. If I am the only person of the right blood type to donate blood to a person who will suffer permanent brain damage without the transfusion, am I obligated to donate the needed blood?  Suppose that if i donate the blood, I will have to remain in bed for two weeks.  These cases are not relevantly analogous to the vaccination case.  Giving blood is time consuming and it can cause discomfort.  Remaining in bed for two weeks is a significant sacrifice. Perhaps I would still be obligated to donate the blood since so much is at stake for the person who needs the transfusion and since I am the only one who can help.  But getting vaccinated is, in most cases, only a minor inconvenience by comparison.

One kind of apparent exception to our principle is illustrated by driving.  In driving, we risk causing harm to others who have not consented to our driving, but, we think, there is no obligation not to drive. This case is not analogous to the issue about vaccination.  That is, refusing to vaccinate oneself despite the risk that one will infect others is not analogous to driving despite the risk to others. We benefit from driving, but we do not benefit from refusing to vaccinate ourselves.  On the contrary, we benefit from vaccinating ourselves, or so we assume, as we will explain.  The cost of refraining from driving to a person living in a typical American city is non-trivial, since public transportation is typically very poor. But the cost of getting vaccinated is very small, as we will discuss later. Furthermore we are obligated to do what we can to reduce the risk of harming someone when we drive, such as by not speeding.  We think people are similarly obligated to reduce the risk of infecting others by getting vaccinated.

We do not attempt to provide a deeper explanation or justification for the principle but believe that once the exceptions have been clarified  and investigated the principle has wide-spread acceptance.


We set out here some of the factual presuppositions that we are making about vaccines in order to apply our principle. Our argument is of the form, if these presuppositions are true of a particular vaccine against a particular disease, then (almost) all adults are obligated to accept vaccination and if they have children under their care have them vaccinated as well.  This is a claim about what is sometimes called “objective” obligation — the obligation one has given the facts — as opposed to, given what one believes to be the facts.  We are saying that if our presuppositions are true in a given case, people have an objective obligation to accept vaccination.

Here are our presuppositions:  The vaccine is (1) “safe” and (2) “effective.” (3) The disease is “life-threatening” or otherwise “seriously threatening” of significant pain, physical or emotional damage, or significant expense or effort to avoid these, to a “significant” subset of the population.  To explain, the safety condition is that there is a very low risk that a person will be harmed due to the vaccine.  The effectiveness condition is that there is a very high probability that the vaccine will prevent a person from being infected by the disease.  The threat condition is that there is a sufficiently high probability that a person who is infected with the disease will suffer serious harm, or that people in a significant subset of the population (such as the elderly or children or people with diabetes) will suffer serious harm.  

Each of these conditions has an associated threshold that it is difficult to be precise about, such as “very low risk,” or “sufficiently high probability.”  But it is often clear enough that these thresholds are met.  For instance, the annual flu vaccine is extremely safe. It carries a risk of less than 1 in 1 million cases of the neurological complication Guillain-Barre syndrome,  And it is reasonably effective at significantly reducing the severity of the flu. And the flu carries significant risk to people with underlying pulmonary weaknesses.  Note that, even with the very low risk and high effectiveness of the flu vaccine, close to half of Americans refuse to get it.

It is tempting to add a fourth condition:  (4) There is not already “herd immunity.”  To explain, so-called herd immunity is reached when enough people have been vaccinated, or have immunity to the disease for some other reason, mainly due to prior infection, that it’s unlikely that an infected person will transmit the disease to more than one other person. But even after herd immunity has been achieved, it can be fragile if people don’t continue to get vaccinated.  Moreover, there can be vulnerable sub-populations that are at risk even after herd immunity has been achieved, some of whom are not able to get vaccinated because of underlying health conditions or because of their age.  

While the general idea of vulnerable populations is familiar, some specifics may be helpful. Who is vulnerable, of course, depends on specific diseases and specific vaccines. In the case of MMR it is the nature of the vaccine itself that creates barriers to vaccination. Women who are pregnant, or think they might be, are not eligible for vaccination. Those with weakened immune systems  due to disease or chemotherapy are vulnerable.Vaccinations of those with a recent blood transfusion are usually postponed for three months or more. Those with tuberculosis will not receive the vaccine. The extended vaccine MMRV which adds Varicella (chicken pox) is only licenced for children older than one year.

Seniors are another vulnerable group both because of their weakened immune systems and because many live in nursing homes. This makes them more vulnerable to various diseases–flu, shingles, pneumonia– and makes it more difficult for them to access vaccination if they are homebound or disabled.

As we are learning during the pandemic, the homeless– the least fortunate among us–are least likely to have access to vaccines such as the meningococcal vaccine which targets meningococcemia, a blood-borne disease.  Given that this population is the least likely to receive adequate health care, it is even more important that they receive vaccinations which will prevent severe diseases.

One doesn’t have to think that any of these populations are more deserving of help than others in order to see that refusing to participate in a fair scheme to help them avoid disease, and also to help the rest of the population avoid disease, is a matter of fairness.  Participation in such a scheme is an obligation for all of us.

Our claim is that in a case in which the three presuppositions are met for a particular vaccine, people are morally obligated to get vaccinated.  There is a significant benefit to the person who is vaccinated, and little risk.  And, importantly, there is a significant benefit to others to whom the person might otherwise transmit the disease, since the disease  is life-threatening or otherwise seriously threatening of significant pain, physical or emotional damage, or significant expense or effort to avoid these, to a significant subset of the population. 

Of course, there can be cases in which these presuppositions are controversial.  What about these cases?  There are widely accepted conspiracy theories about vaccines, and disinformation is spread widely about them.  To the extent that it is reasonable to deny or to doubt the presuppositions in a given case, a person might have an excuse for not accepting vaccination even if doing so is objectively obligatory.  She might not be blameworthy.  Of course, from her perspective, it is not that her blameless ignorance of the facts excuses her.  She thinks she is justified because, if the facts were as she believes them to be, she would be justified.  But whether she escapes blame due to an excuse or a believed justification, the point remains, if we are correct, that she has the obligation to accept vaccination.


In closing, we return to our principle that a person is obligated to refrain from causing harm (or significant risk of harm) to others, and obligated to prevent harm to others, when the costs to the person are relatively small and the benefits great, unless the relevant other(s) give their consent.  We assume that our presuppositions are in place.  That is, we are dealing with a vaccine that is (1) safe and (2) effective in dealing with a specific disease. And (3) the disease is life-threatening or otherwise seriously threatening to a significant subset of the population. What, then, is the harm to others, of not getting vaccinated, in virtue of which, according to our principle, we are obligated to get vaccinated?

We think there are five different harms or risks of harm.  First, non-vaccinators create a risk that they will transmit the disease to others if they get it.  Second they actually do harm to these others if they get the disease and transmit it.  Third, they are weakening the community’s protective herd immunity, even if only to a small degree, which increases the risk to everyone that the disease will spread in the population.  Fourth, if herd immunity has been established by others, who have gone to the trouble of getting vaccinated, the non-vaccinators are free-loading. Finally, fifth, if the non-vaccinators have children and refuse to vaccinate them, then they are creating a risk to their children. For if our presuppositions are true, we are dealing with a disease that is significantly worse than any risk from the vaccine.


David Copp and Gerald Dworkin are both Distinguished Professors of Philosophy Emeritus at the University of California, Davis.