Vaccines and Encephalitis

It is thought that vaccines can, very rarely, cause encephalitis.

“Encephalitis: Irritation and swelling (inflammation) of the brain, most often due to infections.”

IOM Report on Adverse Effects of Vaccines

Encephalitis is actually a table injury in the National Vaccine Injury Compensation Program if it occurs:

within 72 hours of getting a pertussis containing vaccines
within 5 to 15 days of getting an MMR vaccine

And since it is a table injury, then unless another cause is found, “it is presumed that the vaccine was the cause of the injury.”

Most causes of encephalitis are natural infections, including some that are vaccine-preventable. In fact, about 1 in 1,000 people who get measles can develop measles encephalitis.

So the fact that vaccines can, very rarely, cause encephalitis, shouldn’t lead anyone to think that delaying or skipping a vaccine is a good idea.

Autism and Encephalitis

Of course, it isn’t that simple.

The problem?

The misnamed Immunity Education site tries to scare parents into thinking that crying, even excessively, after a vaccine means a child has encephalitis. — The misnamed Immunity Education site tries to scare parents into thinking that crying, even excessively, after a vaccine means that a child has encephalitis.

Anti-vaccine folks claim that an awful lot of things are encephalitis, from crying excessively after getting a vaccine to autism.

Although the Vaccine Information Statement for the DTaP vaccine (it was more common after the older DTP vaccine) does state that children may uncommonly have “non-stop crying, for 3 hours or more” it is not because they have brain inflammation, and the reaction “although unnerving, is otherwise benign.” It is not even a contraindication to getting another dose of DTaP or a later dose of Tdap.

What causes this non-stop crying? It is thought to be a painful local reaction. Fortunately, it does not happen as often with the newer DTaP vaccines.

And autism is not encephalitis.

“That measles infections can cause neurologic side effects on rare occasions is known, but the complication rate for vaccinations is low. After infectious measles encephalitis, risk of an autistic regression has occurred in 1/1000 to 1/10,000 cases. If the trend toward delaying vaccination continues because parents remain misinformed about the MMR, the number of children with neurologic complications of measles or rubella will increase. ”

Chez et al on Immunizations, Immunology, and Autism

Can encephalitis lead a child to have symptoms of autism?

Sometimes.

In addition to natural measles infections, there have been reports of children developing autism after HSV encephalitis, varicella encephalitis, congenital rubella syndrome, and congenital syphilis.

But the great majority of kids with autism do not first have encephalitis. They do not have ongoing brain inflammation.

Saying that encephalitis can cause autism is not the same thing as saying that autism is encephalitis.

Do Vaccines Cause Encephalitis?

And even though encephalitis has long been a table injury for a few vaccines, the 2012 IOM report, “Adverse Effects of Vaccines: Evidence and Causality,” found inadequate evidence to be able to conclude that encephalitis was caused by vaccines.

“Follow-up investigations in that cohort and others, however, found no evidence of a real increased incidence of encephalitis following DTwP. In addition, the most recent IOM report concludes that the evidence is inadequate to accept or reject a causal relationship between diphtheria toxoid-, tetanus toxoid-, or acellular pertussis-containing vaccine and encephalitis or encephalopathy.”

Vaccinophobia and Vaccine Controversies of the 21st Century

That’s not surprising, because follow-up of children studied in the 1980s, from which the original claims about DTP and encephalitis were made, found no evidence of an increased risk of encephalitis.

What about the MMR vaccine?

Again, the IOM report found inadequate evidence, but the problem has always been that “acute encephalitis post-MMR is so rare that it has been impossible to distinguish from the background encephalitis rate of 1 in one million in immune competent hosts.”

Anti-NMDAR Encephalitis

Doesn’t the discovery of anti-N-methyl-D-aspartate (anti-NMDA) receptor encephalitis prove that vaccines cause autism?

“Anti-NMDA receptor encephalitis is a disease occurring when antibodies produced by the body’s own immune system attack NMDA receptors in the brain.”

The Anti-NMDA Receptor Encephalitis Foundation

Often associated with tumors, isolated case reports do correlate anti-NMDAR encephalitis with vaccines. There are so few cases of anti-NMDAR encephalitis though, it is hard to know what they mean, as are the reports of autism developing after anti-NMDAR encephalitis.

What to Know About Vaccines and Encephalitis

Vaccines still don’t cause autism and the latest safety studies report that vaccines probably don’t cause encephalitis, although a few are still listed as a table injury.

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