One commonly repeated incident that propagates and recirculates on anti-vaccine websites is that of a nine-year-old Florida girl who developed an extremely rare neurological condition known as acute disseminated encephalomyelitis (ADEM) five days following her immunization for the flu in November 2013. The incident itself, described in local news accounts, is real:

On November 20, 2013, [the girl’s] parents took her to the doctor where she received her annual flu shot. She would spend the next five days playing with children in the neighborhood. She was on break from school for the Thanksgiving holiday. Her mother recalls putting her to bed on the night of November 25, 2013 … [She] walked into her daughter’s room to check on her. Her daughter was not responding to her calls to wake up, so [she] lightly nudged her. Still there was no response despite [the girl’s] eyes being open … An advanced life support ambulance would transport Marysue to St. Joseph’s Hospital. On the way, she suffered a seizure, according to her mother. Once at the hospital, [the girl] suffered another seizure [and] was now on life support and in the intensive care unit.

The stricken girl was ultimately diagnosed with ADEM, and while most cases of ADEM resolve completely or carry only minor long-term consequences, this case left the patient in a wheelchair and has caused lasting neurological damage. While devastating, the event’s causal relationship to the flu shot is a much more complicated area of science, one that has been misrepresented repeatedly in the anti-vaccine posts that have used this family’s story to advance their fear-driven agenda. A representative example can be found on the conspiracy mill website known as “Natural News”:

National Vaccine Injury Lawyer Leah Durant has reported that ADEM, although rare, can … be triggered by a flu shot. That’s what happened to … a vivacious, active nine year old from Tampa, Florida. On November 20, 2013, [this girl] had a seasonal flu shot. Within days, she became limp, then paralyzed and, as reported by Natural News, “nonverbal, confined to a wheelchair/hospital bed, [and] primarily eating via a g-tube …” According to Myelitis.org, ADEM is a rare auto-immune disease that occurs when the immune system “mistakenly attacks its own brain tissue,” when responding to a vaccination or infection.

A 2016 review of ADEM in the journal Neurology described the disease as belonging to a group of poorly understood conditions known as “immune-mediated demyelinating CNS disorders.” A demyelinating process is one that damages or removes the protective covering surrounding the nerve fibers of the central nervous system, known as a myelin sheath. An immune-mediated demyelinating process is one caused by the body’s own immune system attacking these surfaces, leading to neurological damage:

Acute disseminated encephalomyelitis (ADEM) is an immune-mediated demyelinating CNS disorder with predilection to early childhood … ADEM often occurs postinfectiously, although a causal relationship has never been established … Outcome of ADEM in pediatric patients is generally favorable, but cognitive deficits have been reported even in the absence of other neurologic sequelae … Nationwide surveys of ADEM in Germany, Canada, and Great Britain report incidences of 0.1–0.3 per 100,000 children per year … The median age at presentation of ADEM is 5–8 years, with male predominance.

Because ADEM is an immune-mediated disease, vaccines have long been considered as a plausible trigger for the condition, which is most commonly thought to be caused by the body’s inflammatory response to various viral or bacterial infections.

Evidence for a possible minor link to the MMR vaccine, mentioned above in the Natural News post, has been published, although those conclusions have been disputed, and no widespread epidemiological study has ever found clear evidence of a causal relationship between ADEM and the influenza vaccine, as alleged in the viral story. This is likely why Natural News and other similar outlets rely upon a vaccine injury lawyer, whose livelihood stems from fees garnered from bringing complaints to the National Vaccine Injury Compensation Program, to assert the connection.

A 2015 review of the influenza vaccine’s overall safety concluded that evidence was insufficient to “establish a causal relationship between influenza vaccines and acute disseminated encephalomyelitis”:

The available evidence does not establish a causal relationship between influenza vaccines and acute disseminated encephalomyelitis (ADEM) or transverse myelitis, but the available evidence cannot rule out the possibility of a small increased risk following influenza vaccines. If there is any risk following influenza vaccines, this risk is very low.

In fact, the risk of developing ADEM directly following influenza inoculation may well be lower than the risk of developing ADEM without receiving the influenza vaccine. A 2014 paper that reviewed cases of central nervous system demyelination (like ADEM) following vaccinations of any kind concluded that “The risk of onset or relapse of CNS demyelination following infections against which the vaccines are aimed to protect is substantially higher, and the benefits of vaccinations surpass the potential risks of CNS inflammation.”

Rare neurological disorders which have their onset at around the time a child is of the correct age to receive a vaccine are often asserted to be caused by those vaccines based on temporal proximity, despite a lack of conclusive evidence to draw a mechanistic link. The available evidence does not support a connection between ADEM and the flu vaccine, but the condition is so rare that insufficient data exists to robustly prove a lack of causation at this time. As such, claims that the 9-year-old girl in Tampa developed as a result of the flu shot is unproven.