JurisdictionUnited States

Depending on the jurisdiction, potential defendants in a typical product liability case will include not just the manufacturer of the product, but all others in the chain of distribution, including retailers and suppliers.1 However, exactly who can be held liable, and to what extent, varies widely between states because many states' product liability statutes specify permissible defendants, reflecting the legislature's intention to exclude or limit liability. For example, in Ohio, a "supplier" is liable only if she was negligent or if the product did not conform to a representation made by the supplier.2 A "supplier" is defined by statute as a person who in the course of business "sells, distributes, leases, prepares, blends, packages, labels, or otherwise participates in the placing of a product in the stream of commerce" or "installs, repairs, or maintains any aspect of a product that allegedly causes harm," but does not include, among other things, a seller of real property or provider of professional services.3 Even if the potential defendant qualifies as a liable supplier, she still may not be held liable for all damages unless certain conditions apply.4


Defendants in a strict liability case enjoy a multitude of defenses. In most states, these include traditional tort defenses such as contributory negligence/comparative fault, assumption of the risk, statutes of limitation, and statutes of repose. In some states, misuse of a product (i.e., using the product in manner not intended or foreseen by a manufacturer) can be a defense.5 In other states, a plaintiff must prove that the use of the product was foreseeable as a part of her case.6 Of all defenses, four are particularly common to pharmaceutical cases: the learned intermediary doctrine, the state-of-the-art-product defense, the "unavoidably unsafe" product defense, and the federal preemption doctrine.

The Learned Intermediary Doctrine

The learned intermediary doctrine applies only to failure to warn cases involving prescribed drugs.7 Under the learned intermediary doctrine, the vaccine manufacturer has a duty to warn only the prescribing or administering medical professional of the potential risks of its vaccine, not the patient.8 One of the main rationales behind this doctrine is that only the prescribing healthcare professional is able to understand the significance of the risks involved and to assess the advantages and disadvantages of a vaccine for an individual patient.9

In practice, unless an exception applies, the learned intermediary doctrine requires the plaintiff prove that the warning that the manufacturer provided the prescribing or administrating medical professional was inadequate in order to hold the manufacturer liable. This typically requires deposing the medical professional and inquiring as to whether additional warnings would have changed the provider's decision to prescribe or administer the vaccine. For example, in a 2020 appellate decision10 the U.S. Court of Appeals for the Eleventh Circuit upheld granting summary judgment for Bayer where the prescribing physician testified that, even if the drug's label included the additional warnings, he would have prescribed the drug anyway. As the court explained:

"If the warning is inadequate, or merely presumed to be, the plaintiff must demonstrate that the deficient warning proximately caused the alleged injury." To establish proximate cause, the plaintiff must prove a causal link between the inadequate warning and the prescription decision. Thus, "in cases where a learned intermediary has actual knowledge of the substance of the alleged warning and would have taken the same course of action even with the information the plaintiff contends should have been provided, courts typically conclude that the causal link is broken and the plaintiff cannot recover."11

The one exception to the learned intermediary doctrine that is relevant in the vaccine context is the lack of individualized medical balancing of the risks verses the benefits of a drug. For example, in Davis v. Wyeth Laboratories, Inc.,12 the court held that the learned intermediary doctrine did not apply in an action where the plaintiff contracted polio after receiving an oral polio vaccine at a mass-immunization clinic. The court reasoned that at this mass-immunization clinic, there was not a physician that provided individualized balancing of the risks involved in determining whether the vaccine should be adminis-tered.13 Further, the court noted that the manufacturer knew that the warnings were not reaching the consumer, as the manufacturer took an active part in setting up the mass-immunization program and advertised that all members in the community should take the safe-for-all-ages vaccine.14

In another polio vaccine case, Reyes v. Wyeth Laboratories,15 the court held that the decision in Davis v. Wyeth was not limited to mass-vaccination clinics. The court ruled that the rationale behind Davis v. Wyeth was that the learned intermediary doctrine did not apply to vaccines that were administered "without the sort of individualized medical balancing of the risks to the vaccinee that is contemplated by the learned intermediary" doctrine, where the manufacturer knew or should have known that the vaccine would be dispensed without prescription drug safeguards.16 Thus, the court held that the learned intermediary doctrine did not apply where the vaccine was administered by a public health nurse who did not engage in the individualized medical balancing of the relative risks and benefits of the vaccine.17

"State-of-the-Art" Defense

In many states, it is a defense to a product liability suit when the product's design, manufacture, and labeling (where the warning appears) was state of the art at the time it was designed, manufactured, and labeled.18 There is variation between the states that recognize the state-of-the-art defense, however. In some states, the defense can be a complete bar, while in other states, it is merely admitted as evidence that speaks to whether a safer product or warning was feasible.19

"Unavoidably Unsafe" Products

Comment k to the Restatement (Second) of Torts provides an exception to strict liability in design defect claims:

k. Unavoidably unsafe products. There are some products which, in the present state of human knowledge, are quite incapable of being made safe for their intended and ordinary use. These are especially common in the field of drugs. An outstanding example is the vaccine for the Pasteur treatment of rabies, which not uncommonly leads to very serious and damaging consequences when it is injected. Since the disease itself invariably leads to a dreadful death, both the marketing and the use of the vaccine are fully justified, notwithstanding the unavoidable high degree of risk which they involve. Such a product, properly prepared, and accompanied by proper directions and warning, is not defective, nor is it unreasonably dangerous. The same is true of many other drugs, vaccines, and the like, many of which for this very reason cannot legally be sold except to physicians, or under the prescription of a physician. It is also true in particular of many new or experimental drugs as to which, because of lack of time and opportunity for sufficient medical experience, there can be no assurance of safety, or perhaps even of purity of ingredients, but such experience as there is justifies the marketing and use of the drug notwithstanding a medically recognizable risk. The seller of such products, again and with the qualification that they are properly prepared and marketed, and proper warning is given,

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