On 21 June 2017, the Court of Justice of the European Union (the "ECJ") ruled on a request for a preliminary ruling from the French Supreme Court (Cour de cassation) on the burden of proof faced by patients who have suffered harm from a defective vaccine. The ECJ decided that the defect of a vaccine and the causal link between this defect and a disease can be demonstrated by serious, specific and consistent evidence, in the absence of scientific consensus about a causal relationship (ECJ, 21 June 2017, Case C-621/15, N.W, L.W en C.W v. Sanofi Pasteur MSD SNC, Caisse primaire d'assurance maladie des Hauts-de-Seine and Carpimko).

The background of the request is as follows: Mr. W was injected with a vaccine against hepatitis B. A year later, Mr. W started presenting various symptoms leading to the diagnosis of multiple sclerosis. Mr. W and his family brought proceedings seeking compensation for the damage caused to him by the vaccine on the basis of Article 1386 (currently Article 1245) of the French Civil Code. However, the Paris Court of Appeal held that there was no scientific consensus regarding a causal link between the vaccination against hepatitis B and the occurrence of the disease. On appeal, the French Supreme Court requested the ECJ to interpret Article 4 of Council Directive 85/374/EEC of 25 July 1985 on the approximation of the laws, regulations and administrative provisions of the Member States concerning liability for defective products (the "Directive"). The French Supreme Court sought to know whether that provision stands in the way of national evidentiary rules under which a court may consider that, notwithstanding the finding that medical research neither establishes nor rules out the existence of a link between the administering of the vaccine and the occurrence of the victim's disease, specific factual evidence relied on by the applicant could constitute serious, specific and consistent evidence in support of the conclusion that there is a defect in the vaccine and that there is a causal link between that defect and that disease.

Under Article 4 of the Directive, a person injured by a defective product should prove the damage, the defect and the causal relationship between defect and damage. The ECJ noted that while under the Directive the burden of proof rests on the victim, the Directive does not address how this burden must be met. Hence, the ECJ found that an evidentiary rule based on serious, specific and consistent evidence, in the absence of scientific consensus, does not violate the Directive as it remains for the victim to prove the various elements of his or her case. The ECJ continued that excluding any method of proof other than proof based on medical research would be inconsistent with the objectives of the Directive as this could make it excessively difficult to establish producer liability in many situations.

Nevertheless, the ECJ added that national courts should ensure that the evidence provided is indeed sufficiently serious, specific and consistent to conclude that, notwithstanding the evidence and arguments put forward by the producer, the existence of a defect in the product is the most plausible explanation for the occurrence of the damage. The ECJ also ruled out the use of automatic and irrefutable presumptions based on predetermined factual evidence as this would deprive the producer of the possibility of adducing facts and arguments to rebut that presumption.

In the case at hand, the ECJ considered that: (i) the temporal proximity between the administration of the vaccine and the occurrence of a disease; (ii) the absence of personal and familial history of that disease; and (iii) the existence of a significant number of reported cases in which this disease occurred after such vaccinations could suggest that the administration of the vaccine is the most plausible explanation for the occurrence of the disease and that, therefore, the vaccine would be defective.

This preliminary ruling leaves the pharmaceutical sector more vulnerable to product liability claims as it significantly broadens the range of evidence that individuals allegedly injured by vaccines can rely upon. It is important to note that the ECJ indicated that the evidence submitted under this evidentiary rule can be used not only to establish the causal link but also the defectiveness of the vaccine. However, the ECJ formulated a crucial caveat since such an evidentiary rule can only apply when medical research neither confirms nor rules out the existence of a causal link between the disease and the vaccine.

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