In a recent judgment, the ECJ held that where there is a lack of scientific consensus, proving that a vaccine is defective (and demonstrating a causal link to that damage) may be established by “serious, specific and consistent” evidence, so long as national courts ensure that the application of this evidentiary rule does not result in the burden of proof set out in Article 4 of Council Directive 85/374/EEC concerning liability for defective products (the “Directive“) being disregarded. In short, the use of evidentiary presumptions is permitted to establish a prima facie causal link, but causation by reference to evidence must still be proven by a claimant.


Following a reference made by the French courts in relation to proceedings involving an allegedly defective vaccine, the ECJ was asked to consider:

(1) Whether it was compatible with the Directive to use certain evidential presumptions under French law to prove a causal link between defect in a vaccine and damage suffered by a patient in the absence of conclusive medical evidence.

(2) If so, whether Article 4 of the Directive allowed the use of a “system of presumptions” to allow such a causal link to be found automatically where certain causal indications are shown.

(3) Alternatively, if the answer to the first question was no, whether Article 4 of the Directive then requires conclusive scientific evidence to prove a causal relationship.

Article 4 of the Directive places the burden of proof on a claimant to establish damage, defect and the necessary causal relationship. “Defect” is defined in Article 6, namely that a product is defective if it does not provide the safety a person is entitled to expect, taking into account all circumstances, including (a) presentation of the product, (b) the use to which the product could reasonably be expected to be put, and (c) the time of circulation of the product. Causal relationship is not defined in the Directive.

With this in mind, the Court answered the questions as follows:

(1) Yes. Article 4 allows the use of such presumptions under national evidentiary rules. This permits the consideration of factual evidence to establish prima facie serious, specific and consistent evidence to enable the court to conclude that there is both a defect in the vaccine and a related causal link to the disease.

(2) No. Article 4 does not allow a “system of presumptions” so as to automatically establish presumptions made in the absence of conclusive scientific evidence when certain factual evidence is presented. Some evidence must still be shown by the claimant, presumptions alone are not sufficient to establish the requisite causal link.

(3) In light of the above, the third question did not fall to be considered by the Court.

The Court was clear that had the answer to question 2 have been “yes” this would effectively have reversed the burden of proof set out in Article 4 of the Directive. Accordingly, what will constitute “serious, specific and consistent” evidence must be considered on a case by case basis.