“Vaccine Encephalopathy”. Despite the medical-sounding terminology, it’s a very poorly defined term and is used to describe developmental regression, seizures, and sometimes coma in an infant or young child, beginning 1-14 days following vaccination. The seizures in particular are defined as “febrile” meaning that they’re often associated with fever. This term tends to be used infrequently in the professional literature and has instead been exapted for use in less scientific contexts.
Although there has been considerable public scare over particular vaccines (pertussis, MMR, etc.), the literature on “vaccine encephalopathy” overwhelmingly indicates that it is not the vaccination per se that increases risk in susceptible individuals to seizures and regression but an immune reaction and sometimes the association with fever (hence the term “febrile) . Such seizures are also known to occur with infant infections, indicating that it is the immune reaction that appears to be the common factor, not vaccination. Intriguingly, though the instances seem to be rare, different vaccines induce seizures at different time periods, such that pertussis vaccination typically induces febrile seizures within one day following inoculation, meanwhile MMR induces febrile seizures on average 8-14 days following inoculation .
The prototypical vaccine encephalopathy is remarkably similar to a form of epilepsy called Dravet Syndrome. In this condition, seizures sometimes present in infancy following fever, which can succeed vaccination or other illness . For those who have already developed epilepsy, seizure incidence can also increase following vaccination . Regression follows around the second year of life, after which other seizure types start to arise. Approximately 1 in 30,000 infants will present with Dravet Syndrome and about 2/3rds of those cases will have mutations in the SCN1A gene, a voltage-gated sodium channel [4, 5]. Approximately 1/4th of children with Dravet Syndrome will also be diagnosed with autism, making it a significant syndromic form of autism. A small but significant portion of people with autism also have SCN1A mutations .
A fascinating study by Berkovic et al. (2007) took a look at 14 purported cases of “vaccine encephalopathy” used in a previous study. Through records they confirmed the occurrence of seizure onset within 72 hours of vaccination with pertussis. They then genotyped each of the 14 patients for mutations in the SCN1A gene. They found that 11 of the 14 people indeed had SCN1A mutations, 5 of which lead to probable protein truncation and 6 missense mutations. 9 of the 11 patients also had parental DNA available which was subsequently genotyped, the results of which indicated that all 9 cases were de novo mutations. Ultimately, they found that of the 11 cases, 8 fulfilled diagnosis for Dravet Syndrome (aka, Severe Myoclonic Epilepsy of Infancy, SMEI) and 4 had borderline Dravet’s (SMEB).
Even though the authors acknowledged vaccination as a potential trigger, they nevertheless felt that a change to vaccination protocol with such infants would be useless, indicating that “individuals with such mutations seem to develop [Dravet’s Syndrome] whether or not they are immunised in the first year of life” (p. 491). They admitted, however, that their “experimental design does not address this issue…” (p. 491).
Thankfully, some of the same authors went on to test this hypothesis in a later study, finding that vaccination correlated with an earlier onset of illness . Although the total number of subjects was small (N = 40), the study outcome didn’t indicate a divergence in intellectual outcome, either in terms of regression or intellectual disability, between those in the early age of onset group and those later affected. The authors recanted some of their previous doubts regarding the validity of “vaccine encephalopathy”:
“Although our earlier report suggested that vaccine encephalopathy was not a real disorder, there remains a possibility, because of the apparent temporal association, that DTP vaccination might sometimes trigger the onset of Dravet syndrome. If . . . the observation of the temporal association is valid, a gene–environment interaction might be occurring” (p. 593).
Ultimately, they found that approximately 1/3rd of their Dravet Syndrome patients developed seizures within 72 hours following vaccination, and that disease onset occurred an average of 7.8 weeks earlier than in those who did not develop seizures immediately following inoculation. Nevertheless, the authors conclude that, “there is no rational basis for withholding DTP immunisation for potentially lethal childhood diseases for fear of causing Dravet syndrome or injuring the brain by a direct or presumed immune-mediated mechanism” (p. 597).
While I can appreciate the desire to avoid fearmongering in a culture which is rife with vaccination paranoia, on the other hand, regardless of whether vaccination alters outcome severity, knowingly triggering precocious disease onset seems decidedly unethical. Instead, further detailed study and a more nuanced, informed approach to vaccination schedule in such infants seems warranted, including that of genotyping prior to inoculation. Especially considering the risks of Sudden Infant Death (SID) and mortality due to status epilepticus associated with Dravet Syndrome [ref]. Such revised-vaccination protocols are already in place for infants with certain metabolic disorders.
It has long been postulated that inflammation and even autoimmunity may play roles in susceptibility to epilepsy. The occurrence of fever and infection are documented in some types of seizure onset, and even autoimmune conditions like lupus have increased comorbidity with epilepsy . Some CNS-related autoantibodies have also been noted in epileptic patients, as well as patients with autism [9, 10].
Given the high rate of comorbidity and the overlap in etiology between autism and epilepsy, it causes one to wonder whether vaccinations play a role in age of onset of regressive autism, just as they appear to do in many cases of Dravet Syndrome . In fact, regressive and intellectual disability in autism share tight links with the co-occurrence of epilepsy . However, if regressive autism also shares similar trends with Dravet Syndrome, rates of autism occurrence and severity of symptoms may not ultimately be affected following vaccination, just the timing of onset. Which would explain the results of the many epidemiological studies that have failed to find links between autism risk and vaccination. Should this hold true, it would suggest that, no, parents aren’t necessarily crazy when they see their child drastically regress shortly following vaccination, but nor does it mean that vaccines “cause” autism. As it seems with all of biology, it’s probably far more complicated than that.
However, as a parting gift, I also want to stress to parents that vaccination might also protect against earlier age of autism onset and regression, considering the risks that infection confer in precocious symptom onset as is seen in Dravet Syndrome. Consider if you will a large Danish study published in 2012 by Yun et al. Though they reported that vaccination with the pertussis vaccine conferred a small risk for febrile seizures following 1st and 2nd round inoculations, they also found that inoculation in the larger population was a protective factor against seizures from ages 3-15 months. While we can only hypothesize as to the causes of this finding, if we consider vaccinations’ capacity to prevent infection, it may suggest that vaccines play an even more important role in the prevention of precocious onset of seizures and regressive autism by prevention of those very infections. So while some cases of epilepsy and autism could be triggered earlier by vaccination, vaccination may prevent precocious symptom development in a significantly greater number of cases.
This is why we need more research. We don’t need to panic and forgo vaccinations entirely. We need to demand better research so that we can develop nuanced protocols for individualized medicine. However, just as driving carries with it the risk for car accidents, so too must we accept that vaccinations, no matter how well researched, will also carry a modicum of risk. That is simply a fact of our modern life.