New data show a deadly measles complication is more common than thought

A complication of measles that kills children years after they have been infected is more common than previously thought, according to disturbing data released last month.

The research, presented at IDWeek, the annual meeting of three professional infectious disease organizations, underscores the critical importance of vaccination for everyone who is eligible. Such widespread vaccination, which results in herd immunity, protects children who can't be immunized.

Particularly vulnerable are babies younger than 12 months, who because of their age cannot yet get the vaccine known as MMR, for measles, mumps and rubella.

The complication is a neurological disorder that can lie dormant for years and then is 100 percent fatal. Researchers don't know what causes the virus to reactivate, and there is no cure once it does. The only way to prevent the disorder is by vaccinating everyone possible against measles.

Measles is an extremely contagious respiratory infection caused by a virus. Once common in the United States, it was eliminated nationally in 2000, but has made a comeback, mostly because of the growing number of people who refuse to vaccinate their children or delay those vaccinations, experts say.

The first MMR dose is administered at 12 to 15 months of age. Babies younger than that can get infected with measles and later develop this complication, which is called subacute sclerosing panencephalitis, or SSPE.

Scientists once thought the risk of developing SSPE was about 1 in 100,000. Recent research in Germany among children who got measles before they turned 5 identified a rate as low as one in 1,700.

But the new findings, by researchers at the David Geffen School of Medicine at the University of California in Los Angeles and the California public health agency, found that for babies who get measles before being vaccinated, the rate is 1 in 609.

"This is really alarming and shows that vaccination truly is life saving," James Cherry, a study author and expert on pediatrics and infectious diseases at UCLA's medical school, said. "Measles is a disease that could be eliminated worldwide, but that means vaccinating at least 95 percent of all who are eligible with two doses of measles vaccine in order to protect everyone, including those who aren't old enough to get the vaccine."

In 2014, the United States experienced a record 667 cases of measles, the largest number since the disease's elimination here, according to the Centers for Disease Control and Prevention. One major outbreak occurred primarily among unvaccinated Amish communities in Ohio.

In 2015, there were 189 cases, with 131 cases linked to an outbreak at Disneyland, that put Orange County in California at the center of the worst measles outbreak in that state in 15 years. Twenty-four cases involved children under age 2 who are now at risk of developing the always-fatal SSPE, said Jennifer Zipprich of the California Department of Public Health.

Vaccinating a very high proportion of the population ensures herd immunity, which means those who can't be vaccinated are protected because the disease is less likely to spread. The MMR vaccine isn't recommended until after a first birthday because children retain some of their mother's antibodies until that age, making the vaccine less effective, experts say. Others who can't get vaccinated include people with immune system disorders.

The researchers analyzed cases of California children who got measles between 1998 and 2015, finding that 1 in 1,387 were younger than 5 when they were infected. They identified 17 cases of SSPE during that period, all involving children who had measles before being vaccinated.

The average age of SSPE diagnosis was 12, but the range was from 3 to 35 years. Many of the patients had ongoing cognitive or movement problems before they were definitively diagnosed.

Measles infection causes fever, runny nose, cough, red eyes, sore throat and rash. The virus spreads throughout the body and is usually cleared within 14 days. In rare cases, the virus spreads to the brain but then becomes dormant. Eventually, that can lead to SSPE and result in death.

Among other severe complications of measles, as many as one of every 20 children will develop pneumonia - actually the most common cause of death from measles in young children. And about one of every 1,000 children will develop encephalitis, or swelling of the brain, that can lead to convulsions and can leave the child deaf or with intellectual disability.

Because there is a 5 percent failure rate with the MMR vaccine, a second dose is given to children before they begin school. Measles is so contagious that 95 percent of people need to be vaccinated with two doses to protect those who aren't, experts say. That means all who are eligible, including adults who haven't been previously vaccinated, should receive two doses of the vaccine.

Nearly 92 percent of U.S. children 19 to 35 months old have received the MMR vaccine, according to the CDC. Through Oct. 8, 54 people from 16 states were reported to have measles this year.