The Court of Justice of the European Union has recently ruled that courts may consider vaccines to be the cause of an illness, even in the absence of scientific evidence confirming a link.

In this case Mr W was vaccinated against hepatitis B through three injections administered between 1998 and 1999. In 1999 he began to present with various difficulties which ultimately led to a diagnosis of multiple sclerosis in November 2000 and his death in 2011. His family brought proceedings against Sanofi Pasteur the manufacturer of the vaccine seeking compensation for the damage claimed to have been suffered due to Mr W's having been administered with the vaccine in question. They pleaded that the period in between the vaccination and the appearance of the first symptoms of MS in conjunction with the lack of any personal or family history of the disease are such as to give rise to serious, specific and consistent presumptions as to the existence of a defect in the vaccine and as to there being a causal link between the injection of the vaccine and the occurrence of MS.

The case was brought before the Court of Appeal in France, which ruled that there was no scientific consensus supporting a causal link and no evidence of a causal link between the hepatitis B vaccine and Mr W's MS and dismissed the action. This judgment was appealed and brought to the French Court of Cessation, which took it to the European Court of Justice (CJEU) based on the EU Directive on Liability for Defective Products (Directive 85/374/EEC).

The CJEU held that Article 4 of the Directive (which puts the onus on the injured person to prove the damage, defect and causal relationship) should not be interpreted as not precluding national evidentiary rules such as those at issue in the main proceedings so that here a national 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, certain factual evidence relied on by the applicant constitutes serious, specific and consistent evidence enabling it to conclude that there is a defect in the vaccine and that there is a causal link between that defect and that disease.

The CJEU went on to state that the Directive cannot be interpreted as allowing for evidential presumptions if there is no medical research that the existence of a causal link between the defect attributed to the vaccine and the damage suffered by the victim will always be considered to be established when certain predetermined causation-related factual evidence is presented.

The ruling states that courts must ensure that evidence is "sufficiently serious, specific and consistent to warrant the conclusion," having also considered available evidence and arguments made by a vaccine's producer, to then decide that a vaccine is the most plausible explanation for any damage to health.

The court's decision is not a ruling on Mr. W.'s case but provides guidance for all courts within the EU considering similar issues. When there is scientific uncertainty, and no clear evidence to either side of the causation equation, the plaintiff does not automatically lose their case for inability to prove the link scientifically, and can use external factors (like time and lack of family history) to convince the court to find a link anyway. However the CJEU strongly emphasized that manufacturers should be given opportunity to present counter evidence, including countering scientific evidence

It will be interesting to see how the decision of the CJEU will be applied in future cases involving "vaccine injury".