The EU's highest court said that if the development of a disease is timely to the person's receiving a vaccine, if the person was previously health with a lack of history of the disease in their family and if a significant number of disease cases are reported among people receiving a certain vaccine, this may serve as enough proof.
The ruling stemmed from the case of a French man known as J.W. who was vaccinated against hepatitis B in 1998 and developed multiple sclerosis a year later. Multiple sclerosis is a neurological disorder in which the body's own immune system attacks the brain and spinal cord. The disease scars nerve tissue and causes a range of symptoms, from vision problems to paralysis. J.W. died in 2011.
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 the man's multiple sclerosis, therefore dismissing the action.
This judgment was appealed and brought to the French Court of Cessation, which took it to the European Court of Justice.
The Court of Justice said that "specific and consistent evidence" relating to timeliness, a prior healthy status, lack of family history and multiple cases may prove to be enough, according to a statement
. J.W.'s case referred to the first three criteria.
The ruling added 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 J.W.'s case but provides guidance for all EU courts considering similar issues.
The EU court is authorizing national courts to make such judgments about causality themselves, based on evidence they are presented with, without reliance on expert opinion, said Professor Tony Fox from the pharmaceutical medicine group at King's College London.
In a statement, a representative from Sanofi Pasteur said: "It is not our role to comment on this legal decision. However, Sanofi Pasteur wishes to reiterate that its vaccines are safe and effective and protect against infectious diseases. Our hepatitis B vaccines are safe and well tolerated. They have been approved by Health Authorities and are marketed for more than 30 years."
The decision drew criticism from experts.
"No causal link exists" between the hepatitis B vaccine and multiple sclerosis, "but a few cases after vaccination would not be surprising, especially when administered to teenagers, just before the age of onset age for many MS sufferers," said Keith Neal, emeritus professor in the epidemiology of infectious diseases at the University of Nottingham.
"What they are saying is, the vaccine is responsible for the patient's MS if it can't be proved it isn't, and that is virtually impossible given what is worded. Potentially, this ruling affects all drugs and threatens the development of new drugs."
Peter Openshaw, president of the British Society for Immunology and professor of experimental medicine at Imperial College London, said "it is very concerning that the European Court of Justice has ruled that judges can consider whether a vaccination led to someone developing a medical condition, even if there is no scientific evidence to support this."
"The scientific evidence does not support a link between the hepatitis B vaccine, or any other vaccine in current use, and multiple sclerosis," he said. "To say that there is a link between any vaccine and multiple sclerosis and at the same time to admit that there is no scientific evidence of such a link is illogical and confusing to the public."
The prior health of the patient, absence of family history and supposed close temporal relationship could all be coincidental, Fox said.
"The only alleged evidence that would be worth taking seriously is the alleged numbers of other similar cases," he said. "Those data should be capable of detailed case comparisons for consistency, and probably also orthodox epidemiological study."
But without such a study, Fox added, "one might just as well say, 'If this vaccine causes MS, then why is it that millions of people have been vaccinated and did not get MS? And why are there so many people with MS who have never had this vaccination?' "