Jaxon Abalahin was a happy and seemingly healthy 5-year-old who had just returned home from what his mother would describe as “a great day at kindergarten” in February of 2005.

He then suddenly had difficulty speaking. His head began to dip forward in a kind of fast nod every few seconds.

His alarmed parents — Paula and Oscar Abalahin of Port Orchard, Washington — took him to a pediatrician, who referred them to a pediatric neurologist, who began a long series of tests. The neurologist put Jaxon on anti-seizure medicine, but his condition inexorably deteriorated.

The once athletic little boy with a precocious love for golf and basketball began having difficulty walking. He repeatedly fell down where a short time before he would have been gleefully dashing about. He had difficulty swallowing.

“You had to be really careful feeding him,” the father recalled. “He was just deteriorating.”

His speech slurred, then he ceased talking altogether. He seemed to understand what was said to him but he became unable even to nod voluntarily to indicate yes or no.

“You would ask a question, ‘How are you doing?’” the father remembered. “Often, he would just look at you.”

The deterioration continued and the doctors still had no diagnosis, much less a treatment. The mother went back through Jaxon’s medical records to before they had adopted him, in 2001. He had been an 18-month-old foundling in an orphanage in the Philippines who had initially been given the surname Normales because that was the name of the street where he had been discovered, abandoned at birth.

His adoptive mother now came upon something in the records the doctors had not considered.

“The only thing nobody looked at was that when he was a kid he had measles,” the father later told The Daily Beast.

The mother began an online search for anything related to the measles Jaxon had contracted at 7 months. He had appeared to make a full recovery, but she wondered if it still might explain his sudden illness nearly five years later. She came upon a rare, deadly and seemingly incurable condition.

“We didn’t want it to be that,” the father later said.

The parents asked if Jaxon’s measles could have resulted in an invariably fatal condition called subacute sclerosing panencephalitis [SSPE]. The doctors conducted blood tests and a spinal tap and an EEG.

“It all came back positive,” the father recalled. “Now we know what it was, [but] there was still no treatment for it.”

Their doctor then learned a physician in Southern California had developed a protocol for another child who had developed SSPE after a measles outbreak there in the early 1990s. The protocols stabilized Jaxon for a time.

“It wasn’t getting worse but it wasn’t getting better,” the father said.

But then, in 2008, he began to grow steadily worse. The parents understood the end might be near and they sought to bring Jaxon home, so he could die there.

“In his own house,” the father said.

But Jaxon was now on a respirator and he remained in the hospital. His mother had lifted him in a final embrace at the end. He died in her arms, which the father later figured could be viewed as a more profound way of dying at home.

“A house is just a building,” the father later reasoned.

That was in 2008. The parents have since sought to alert other parents to the rare, but terrifying and devastating complication that makes vaccination all the more necessary.

“Keeping Jaxon's legacy alive,” the father said. “Keeping other kids from getting it.”

SSPE is now considered to be somewhat less rare than was once thought, developing in 1 of every 600 infant measles cases, generally between 4 and 8 years after infection. It then suddenly appears without warning, as if SSPE were a bomb that had been tick, tick, ticking that whole time.

Earlier victims include a 9-year-old girl from Stockton, California who, died in 1998. Her mental symptoms were initially more pronounced than the physical ones.

“As in this case, patients are often misdiagnosed with psychiatric disorders,” a study of this case and SSPE in general reads.

The girl was an identical twin and her sister remained healthy. The same was true of another case involving identical twins. The scientists were mystified.

“Identical twins presumably present identical genetic backgrounds, had similar antibody panels, would be infected with the same viral strain, and experience the same exposures,” the paper noted.

In 2015, a 14 year-old Oregon boy died, having contracted measles when he was a 1-year-old in the Philippines. The first signs of SSPE did not appear until a decade later.

“Before the onset of his neurologic illness, the patient had been a straight-A, fifth-grade student who played soccer and basketball,” a CDC report would recount. “The patient began to struggle with homework, drop utensils, and doze off during meals, eventually progressing to falling asleep while walking.”

The report continues, “During the subsequent month, his mother reported that he was less alert and sometimes seemed confused. He experienced myoclonic jerks and involuntary hand and arm movements, which became increasingly frequent, and his coordination deteriorated. He missed 3 weeks of school and required a home tutor. His appetite decreased, and he lost 12 pounds but remained playful and interactive.”

The report further says, “A pediatric neurologist was consulted. No family history of neurologic disease was reported. The initial evaluation included a lumbar puncture and magnetic resonance imaging of the brain, both of which were unremarkable. An electroencephalogram (EEG) was abnormal, with frequent, high-amplitude bifrontal slowing, a nonspecific finding. Despite extensive evaluation, the cause of the neurologic degeneration was not identified.”

And it goes on, “During the following month, the patient’s cognitive and motor skills declined further and included the onset of repetitive behaviors, as well as inability to sit still, frequent falling, and asking seemingly meaningless questions. He became aggressive and could no longer be tutored… He began to shuffle and walk on his toes; he eventually refused to walk. He cried continuously, became increasingly aggressive, and began sleeping for longer periods. Although he was responsive at that time, his speech became difficult to understand; eventually he could say only a few words… He experienced worsening spasticity and rapid decline in mental status; he became incontinent and was unable to eat or drink. He did not fix on or follow objects, and he no longer appeared to recognize his family members’ faces or voices.”

Four months after the onset of the symptoms, the boy was admitted to a hospital. The report continues, “He had abnormal movements of the arms and legs, was unresponsive to questions, and unable to follow commands.”

Tests determined that he had SSPE.

“Because no specific therapy was available, the patient was discharged after 14 days and died in home hospice care 43 months later, in 2015,” the report says.

The report, Notes from the Field: Subacute Sclerosing Panencephalitis Death — Oregon, 2015, concludes, “This case underscores the importance of maintaining high population immunity, through routine administration of 2 doses of measles-containing vaccine to all eligible children.”

The authors included Dr. Paul Cieslak, presently the Oregon medical director for communicable diseases and immunization. A current measles outbreak in the Portland area and in adjoining section of Washington has spread to 50 people or more.

Cieslak avoids even the appearance of being a fearmonger. He is careful to say that SSPE remains a rare condition. But is he also of the strong opinion that no child should have to suffer such a horror if it is at all preventable.

And it is.

As Jaxon's father said this week, “If you don't get measles, you won't get SSPE.”

The father knows from the loss of his son that the danger we should concentrate on is not that of immunization but of the disease.

“Once you have measles, it never leaves you,” Oscar Abalahin said. “It never goes away.”

Anybody's child who does get measles then has to wait a decade or more before the threat of SSPE — however remote — has completely passed.

Get the shot.

Or maybe tick, tick, tick.