Here’s a question anti-vaxers may want to consider:

Can the parents of an unvaccinated child be held liable if their child becomes infected with a vaccine-preventable disease which then spreads from their child to another child or children?

Yes, they can.

In fact, for over 125 years, courts in this country have recognized a cause of action for negligent transmission of an infectious disease. In the first reported case (New York, 1884) the defendant infected the plaintiff with whooping cough. Cases since then have run the gamut: smallpox, tuberculosis, unspecified “venereal disease,” typhoid fever, scarlet fever, diphtheria, hepatitis, herpes, gonorrhea, HIV. If your favorite infectious disease is not on this list, don’t worry. The disease may vary, but the legal principles remain the same.

You’ve got WHAT?

As the previous paragraph suggests, one need look no further than plain old negligence for an entrée to the courts — the same legal principle that forms the basis of actions arising out of automobile accidents and slip and fall cases.

Here’s how the Court of Appeals of Maryland described the basic law of negligence and its application to infectious diseases:

The traditional elements of a cause of action in negligence may be stated as:

  1. A duty, or obligation, recognized by the law, requiring the person to conform to a certain standard of conduct, for the protection of others against unreasonable risks.
  2. A failure on the person’s part to conform to the standard required: a breach of the duty ….
  3. A reasonably close causal connection between the conduct and the resulting injury ….
  4. Actual loss or damage resulting to the interests of another ….

The notion of duty is founded on the ‘responsibility each of us bears to exercise due care to avoid unreasonable risks of harm to others.’ … ‘When a reasonable person knows or should have known that certain types of conduct constitute an unreasonable risk of harm to another, he or she has the duty to refrain from that conduct.’ …

One who knows he or she has a highly infectious disease can readily foresee the danger that the disease may be communicated to others with whom the infected person comes into contact. As a consequence, the infected person has a duty to take reasonable precautions—whether by warning others or by avoiding contact with them—to avoid transmitting the disease. ‘[As an example] if defendant knew that he was afflicted with smallpox it then became and was his duty to keep away from other persons, or should other persons approach him to notify them of the fact so that they might protect themselves.’

B.N. v. K.K., 538 A.2d 1176 (Md. Ct. App. 1988)(citations omitted)(emphasis added).

In this case, K.K., a doctor, transmitted genital herpes to B.N., a nurse with whom he worked at Johns Hopkins Hospital. (Hence the discrete initials instead of the names of the parties, although that privilege is not always granted to the litigants in STD cases.) Dr. K.K. and Nurse B.N. had a sexual relationship of several months’ duration during which time Dr. K.K. — rather ungallantly — failed to tell Nurse B.N. about his infection, even though he knew his diagnosis and on at least one particular occasion knew that he had an active case.1

While the facts were unique to the case under consideration, the Maryland appellate court correctly stated the law of negligence generally applicable in the 50 states. Some courts have added that the duty to exercise due care not to infect others is also grounded in the state’s interest in the prevention and control of disease. (Caveat: each state’s courts have the jurisdiction to create variations on the law of negligence, so, as has been said on this blog before, your results may vary.)

But what if one doesn’t know he has a contagious disease?

Actual knowledge is not required, although it makes for easier proof. Courts have found that in certain circumstances the infected person should have known, or, as it is sometimes put, he had constructive knowledge of his disease. This can be established on the basis of symptoms alone, without a confirming medical diagnosis, particularly where symptoms of the disease are well publicized, such as is true of HIV/AIDS infection and genital herpes.

Note that a “reasonable person” is the standard — what a reasonable person knew or should have known. Thus, being merely unaware (in cases where the “reasonable person” would have known) or willfully ignorant of the disease is no excuse.

Once a duty to act with due care is established through actual or constructive knowledge of one’s disease, the infected person is charged with, at the least, warning those with whom he comes in contact that he has a communicable disease (allowing them to choose to stay away) or himself choosing not to engage in activity which would spread the disease to others. If he fails to do so, the second element of negligence — breach of his duty — is established.

A tougher problem might be to show that the diseased person’s conduct was the cause in fact of the plaintiff’s injury, the third element of proof in a negligence case. Even though she catches the same infectious disease as is suffered by the defendant, the plaintiff must still show the defendant was in fact the source of her disease. Depending on the disease, this can be accomplished through expert testimony concerning, for example, how contagious the disease is, the incubation period, and DNA testing of the disease strains.

Finally, there must be actual damages, and there usually are, in the form of medical expenses. (The collateral source rule prevents the offset of health insurance payments against the plaintiff’s recovery.) In cases where the defendant’s conduct was particularly egregious, punitive damages might be awarded. Other types of damages are discussed below.

No two negligence cases are exactly alike. There will always be factual variations to weigh in determining liability. In general, however, negligent transmission of infectious disease cases will turn on two issues: (1) Did the defendant know, or should he have known, he was contagious, and (2) Was he the cause in fact of plaintiff’s disease. Once those two are established, the defendant’s lack of due care will almost always be a given, as will at least some damages. Of course, in some cases the facts may show contributory negligence, or even consent, by the plaintiff.

While negligence is the most common, and easiest to prove, claim against a defendant who has transmitted an infectious disease, it’s not the only one. Actions for fraud, intentional infliction of emotional distress, the tort of battery, other forms of intentional tort, and actions based on premises liability (for failure to warn of a communicable disease on one’s property) have all been the subject of suits based on the contraction of an infectious disease.

Some states have a law making it a crime to intentionally transmit HIV to another through sexual contact. If that is not the case, the crimes of battery and reckless endangerment may offer the possibility of prosecution for any infectious disease transmission given the requisite proof of intentional or reckless conduct.

So sue me! 

So let’s apply these lessons to a perennial topic at SBM — parents who refuse to vaccinate their children because of unwarranted fears about vaccine safety. What part such children might be playing in the current pertussis epidemic is a question under investigation by public health authorities, as pointed out in a recent post by Dr. Steve Novella.

First, note that in the case of vaccine-preventable childhood diseases, it’s not the child who is calling the shots. (Sorry!) Children under a certain age (usually 18) are deemed legally incapable of making decisions about their health care. The parents make those decisions and it is the parents who are legally responsible for the consequences of their decisions.

Of course, as the standard for determining negligence is what a “reasonable person” in the same or similar circumstances would do, how could that standard ever be applied to children? The “reasonable toddler?” No such thing.

Second, it does not matter WHY the parent chose not to vaccinate in establishing liability. The parent may have exercised his statutory privilege of opting out for religious or philosophical reasons, but that’s not the equivalent of a “get out of jail free” card for all the consequences of that decision.

In fact, it can help the plaintiff establish liability by showing that the parent knew, or should have known, her child was vulnerable to vaccine-preventable diseases and that this, in turn, made it more likely that her child would transmit these diseases to unvaccinated, not fully vaccinated and even vaccinated children.

In one New England Journal of Medicine2 article the authors point out:

  • Children with non-medical exemptions are at a greatly increased risk for acquiring and transmitting vaccine-preventable diseases;
  • In one study, at least 11% of nonexempt children who acquired measles were infected through contact with an exempt child;
  • Outbreaks of vaccine-preventable disease often start among persons who refused vaccination, spread rapidly within unvaccinated populations, and then to other subpopulations, such as vaccinated children.

In cases where there is not a confirmed diagnosis, I would argue that reasonable parents should have been on high alert for symptoms, given their child’s increased susceptibility. While the parent of a vaccinated child could be excused for not thinking his child, broken out in little blisters, might have chicken pox, the argument can be made that the parent of an unvaccinated child shouldn’t be given that consideration.

As one treatise states:

The defendant’s membership in a group at high risk for development of a particular infectious or contagious disease, his or her involvement in patterns of behavior likely to result in contraction of a disease, and/or his or her exposure to a disease in circumstances likely to lead to contraction of the disease are additional factors which may assist the plaintiff in establishing constructive knowledge. If any combination of the factors stated above would put a reasonable person on notice of the need to inquire further, the defendant will be charged with constructive knowledge of any facts reasonable inquiry would have disclosed.

22 Causes of Action 1, at 18 (Westlaw, accessed June 4, 2010).

“Group at high risk?” “Behavior likely to result in contraction of a disease?” Sounds like a description of the unvaccinated child.

An insolent question

With all of this in mind, we turn to a hypothetical posed by Dr. David Gorski:

What would the liability be of the parents of a child who refused to vaccinate if their child infected other children, leading to serious harm (such as measles encephalitis). Let’s say the causation could be proven very strongly, for instance by the sequence of the measles virus in the unvaccinated child matching exactly the measles that infected and harmed other children. Say the children who were harmed were fully vaccinated against MMR (remember, MMR is not 100% effective).

Slam dunk, Dr. Gorski! With a few caveats.

Certainly, if the parents knew, or should have known from symptoms, that their child was infected with measles and then put him into a position where he might infect other children, and causation has been established as you suggest, then the parents would be liable to the injured children for their pain and suffering and to their parents for all medical and other expenses incurred in taking care of their ill children. If the encephalitis had lasting effects, the defendant parents would also be liable for the continuing care of the children, the children’s future wages, and the parents’ loss of their children’s help and support. If any of the children actually died, the amount of loss would depend on the wrongful death law of the state where this occurred as the method for calculating those losses varies from state to state. Then there is the possibility of punitive damages.

In other words, this could run into hundreds of thousands, even several million, dollars, depending on the number of children injured and the extent of their injuries.

But … factual variations might influence the outcome. If the parents of the unvaccinated child knew the other children were vaccinated, the finder of fact (either the jury or, if a bench trial, the judge) might determine they were not negligent. It would depend on whether a reasonable person should know the vaccine is not 100% effective. If the parents of the injured children knew or should have known the unvaccinated child had the measles, and the uncertain effectiveness of the vaccine, then their own negligence might reduce their recovery, but not that of the children. And so on.

“Chicken pox parties” present an interesting case. For the parent supplying the diseased child to the “party” the prospect of liability should be particularly troubling. She is not negligently spreading her child’s disease — she is intentionally spreading it. Intentional torts automatically subject the defendant to the possibility of punitive damages, which are usually based on the defendant’s net worth. The whole point is to make sure the defendant is financially punished for her actions — in other words, to take enough money that it hurts.

Punitive damages are on top of actual damages, such as medical bills, and pain and suffering. As in the above hypothetical, while the recovery of parents subjecting their children to the virus can be reduced — perhaps eliminated in this case — because of their actions, the award to the children cannot, and it is the children who are entitled to punitive damages. It could turn out to be a very expensive party.

And what about the physician? What role does he or she play? Well, possibly the role of “defendant.” Courts in a number of jurisdictions have found that in certain circumstances a physician is liable to a third party who contracts a contagious disease from the physician’s patient. One of these circumstances is the physician’s failure to inform the patient how to avoid the spread of the disease, such as by avoiding specific at-risk conduct. Another is giving the patient inadequate or incorrect information. The physician does not need to know that this third person even exists and the third person does not have to rely on the physician’s incorrect advice to hold the physician liable.

As one court in Pennsylvania said,

the duty of the physician treating a patient with a communicable disease is to prevent the spread of the disease, not for the benefit of the patient, whose health has already been compromised, but for the benefit of those third parties ‘within the foreseeable orbit of risk of harm.’

Troxel v. A.I. DuPont Institute, 450 Pa.Super. 71, 675 A.2d 314 (Pa. Super. 1996)(citations omitted).

I would argue that this duty to third parties requires a physician to warn the vaccine-refusing parent, and the parent who chooses the “alternative” vaccine schedule (a la Dr. Bob), of not only the heightened risks to her child resulting from vaccine refusal or delay, but also the risks to other persons to whom her child could spread disease. This information would include the symptoms of the preventable disease and how to avoid infecting others. Otherwise, beware of small third parties bearing service of process coming at you from “the foreseeable orbit of risk of harm.”

Closing argument

In sum, the state’s interest in preventing the spread of communicable diseases manifests itself not only in mandatory vaccine laws, but also in impressing a duty to avoid the spread of disease on those who are infected with, or who are at high risk for contraction of, a communicable disease. Where the diseased are children, the responsibility for fulfilling this duty falls on the parents. As well, physicians of high risk or infected patients must properly instruct patients in avoiding transmission of disease to others. Those who breach their duty to avoid the spread of communicable disease may be liable to those injured for damages.

Parents who refuse vaccination may be willing to forsake their children’s health for their religion or their philosophy, but once that choice adversely affects someone else’s child, they will have to pick up the tab.


1. I have no sympathy for Dr. K.K., but do note that it must be a huge bummer for one’s negligent transmission of genital herpes case go all the way to the state court of appeals and be immortalized in published case law.  Future defendants in such cases might want to consider settlement.

2. Omer SB, Salmon DA, Orenstein WA, et al., Vaccine Refusal, Mandatory Immunization, and the Risks of Vaccine-Preventable Diseases, N Engl J Med 2009; 360:1981-1988.



  • Jann J. Bellamy is a Florida attorney and lives in Tallahassee. She is one of the founders and Board members of the Society for Science-Based Medicine (SfSBM) dedicated to providing accurate information about CAM and advocating for state and federal laws that incorporate a science-based standard for all health care practitioners. She tracks state and federal bills that would allow pseudoscience in health care for the SfSBM website.  Her posts are archived here.    

Posted by Jann Bellamy

Jann J. Bellamy is a Florida attorney and lives in Tallahassee. She is one of the founders and Board members of the Society for Science-Based Medicine (SfSBM) dedicated to providing accurate information about CAM and advocating for state and federal laws that incorporate a science-based standard for all health care practitioners. She tracks state and federal bills that would allow pseudoscience in health care for the SfSBM website.  Her posts are archived here.