A healthy man was struck by a life-threatening inflammation of his brain and spinal cord after just one dose of a Covid vaccine.

The unnamed 60-year-old sought help from medics in Paris, France after suddenly developing walking problems and mental confusion, four weeks after receiving a dose of AstraZeneca’s Covid jab.

Brain scans revealed he was suffering from meningoencephalitis—a life threatening swelling of the brain and the tissue surrounding the brain and spinal cord—according to doctors who shared his tale in a medical journal.

While the condition can be caused by health problems like an infection or blood cancers, analysis of the man’s brain tissue showed no signs of any viruses or other disease that could be responsible

This led medics to believe that the man’s swelling was caused by his Covid vaccination, specifically his immune system over-reacting to the jab.

They then diagnosed him with postvaccinal encephalitis, dangerous brain swelling following a jab.

The man, who suffered two bouts of brain swelling while in the care of the medical team, was treated with special drugs to suppress his immune system for six months until his symptoms were under control.

Doctors, who reported the case JAMA Neurology, said the man had made an almost full recovery three years after

However, they noted he continued to suffer from ongoing mild problems with his attention span.

The patient originally showed significant improvement after being treated when he first suffered symptoms four weeks after getting the jab.

However, he returned with the same walking and mental confusion problems three months later which when medics conducted the brain biopsy and put him on six months of medication.

Medics said the relapse showed the importance of sustained drug treatments for such patients as well as ‘prompt diagnosis and aggressive treatment’.

Encephalitis after Covid vaccines have been reported before.

A study published in 2023 on 65 patients found AstraZeneca was the most common vaccine brand linked to the reaction, accounting for over a third of cases.

The authors of that report highlighted that what exactly causes vaccine induced encephalitis to occur in some patients is not yet understood.

However, they added that majority of cases have made a full recovery.

While the team behind the most recent report did not specify when the man received the Covid jab it is likely to have been in 2021.

Researchers tasked with investigating the adverse reaction believe it occurs due to the modified cold virus lurking in the jab acting like a magnet to a type of protein in the blood called platelet factor 4. Platelet factor 4 is normally used by the body to promote coagulation in the blood, in case of injury. Then, in rare instances, the body’s immune system confuses platelet factor 4 with a foreign invader and releases antibodies to attack it in case of ‘mistaken identity’. These antibodies then clump together with platelet factor 4, forming the blood clots that have become so heavily linked with the jab, according to their theory

This followed reports of a small number of patients suffering an extremely rare but potentially deadly blood clotting reaction.

Called thrombosis with thrombocytopenia syndrome (TSS), this is a medical condition where a person suffers blood clots along with a low platelet count. Platelets typically help the blood to clot.

The complication—missed in initial safety trials due to its rarity but now listed as a potential side effect of the jab—has also previously been called vaccine-induced immune thrombotic thrombocytopenia (VITT).

Health officials first identified cases of VITT linked to AstraZeneca’s jab in Europe as early as March 2021, just over two months after the vaccine was first deployed in the UK.

However, it wasn’t until April that year that evidence became clear enough that the jab started to be restricted.

Officials first stopped dishing out the jab to people under the age of 30. They then expanded this to only people over 40 in May 2021.

As the vaccine still worked against Covid, it was still deemed worth giving to older Britons who were at greater risk of death or injury from falling ill with the virus.