Entitlement – Cerebral Anaphylaxis and Seizure caused by MMR & DTaP


Price v. HHS, (Fed. Cl. Spec. Mstr. Oct. 29, 2015) (Gowen, SM)

The Court found that Petitioner proved a Table Anaphylaxis—within the required four hours of receipt of the DTaP and MMR vaccinations, two minutes in this case and that the ongoing seizures were a result of the anaphylactic injury.

Petitioner’s expert testified that Petitioner experienced a “focal” cerebral anaphylaxis based upon the localized abnormalities on the EEG that was done the following day.  The mechanism, supported by a textbook, was this: A susceptible person who has a predisposition to develop IgE antibodies to a specific antigen is initially sensitized by exposure to that antigen.  Upon subsequent exposure to the same antigen, the person can rapidly experience symptoms ranging from rhinorrhea to death.   The petitioner’s expert also explained that anaphylactic reactions are often biphasic, with symptoms recurring, despite appropriate treatment, within two to eight hours of the initial rapidly occurring event.  In particular, both the vaccine antigens and gelatin, a component of both vaccines, could cross the blood-brain barrier attached to IgE receptors on the mast cells in the brain, cause a cross linking of those mast cells in the brain, and produce the rapid release of the anaphylactic agents (histamines, leukotrienes, peptides, and cytokines) in the mast cells, all within five minutes.  The Special Master found that this was a reasonable and persuasive theory.

Regarding the seizures, Petitioner’s expert testified that the initial seizure occurred as a result of the aforementioned mechanism and that the subsequent seizures, beginning a little over four hours later, were explained by a secondary or biphasic hypersensitivity reaction that is not the immediate anaphylactic reaction.  Apparently, seizures occur in 1-2% of anaphylactic reactions.  Thus, the anaphylaxis was a brain anaphylaxis which resulted in an encephalopathy, (though not a table encephalopathy), causing epilepsy.

The mechanism for the seizures was that the anaphylactic reaction in the central nervous system was caused by the triggering of degranulation of mast cells also present in the brain. Upon exposure to a particular antigen, some people develop IgE antibodies rather than the IgG or IgM when class switching occurs.  IgE causes that person to have an allergic response to a subsequent exposure to that same antigen.  The Special Master also accepted this testimony.

Respondent’s expert believed the most common presentations of anaphylaxis, including cutaneous, respiratory, or cardiovascular symptoms, were not present in this case, and he did not believe that seizures could be part of an anaphylactic phenomenon.  Ultimately, he said he was relying on epidemiology which has not identified a signal that would, for example, raise the relationship between a vaccine and the onset of epilepsy from 1.00 to 1.20.

With regard to prong 2, the Special Master observed that differential diagnosis is a well-accepted medical methodology for determining diagnoses and causation, and it has been accepted by multiple courts under a Daubert analysis.  Thus, Petitioner’s expert’s differential diagnosis of an anaphylactic reaction to the vaccinations was both reasonable and persuasive. He provided a logical cause and effect explanation of the mast cell mechanism that likely resulted in a central nervous system anaphylaxis in a child who received vaccine antigens to which he had previously been exposed from prior vaccinations of the same type.

While Respondent’s expert testified that he thought that Petitioner suffered an idiopathic seizure, he did acknowledge on cross-examination that it was plausible to say that the chances of the child suffering an idiopathic event within two minutes of receipt of a vaccine would be on the order of one in fifty million. The court held that, as demonstrated by Petitioner’s expert’s testimony and supporting literature, the likelihood of a biphasic anaphylactic reaction to the vaccines was greater than one in fifty million, and in fact, is more likely than not.   Timing was appropriate for an anaphylactic reaction.

The Court rejected the proposed alternative cause of an unknown gastrointestinal illness.

The Court then noted that Petitioner had proven both a table and off-table anaphylaxis.  This was thought to be necessary, because the QAI illustration of anaphylaxis did not include the term seizure, but more generally described the most common manifestations of anaphylaxis, including severe respiratory and cutaneous symptoms at times leading to death.   The Court held that, in reviewing the aid to interpretation of anaphylaxis, the definition provided is illustrative of the condition but not restrictive, as is for example, the definition of a table encephalopathy.

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