The Double Whammy of Measles

“He who hesitates is lost.” - Cato

Why another blog on measles, when only two months ago the blog: Fueled by Vaccine Hesitancy, Measles Is Going Viral, was posted? Two reasons: 1) it’s time for an update on the U.S. outbreak, and 2) multiple important publications appeared on November 1st that shed light on how the measles virus compromises immunity, not only to itself but also to other pathogens—the “double whammy”.

First, the good news. On October 4, 2019, the Centers for Disease Control and Prevention (CDC) declared that the measles outbreaks in New York were officially over. This set the stage for the U.S. maintaining its World Health Organization (WHO)-certified measles-free status that was set to expire in six days. By then, the CDC had confirmed 1,249 cases of measles between January 1 and October 4, 2019. This year already has logged in the greatest number of measles cases since 1992. While cases have been reported in 31 states, 75% of them were linked to outbreaks in New York City and New York state. Most of the cases were among unvaccinated children in Orthodox Jewish communities. In both instances, the outbreaks were traced to unvaccinated travelers from Israel who brought the measles virus with them at the beginning of October 2018.

As was described in the September 6 blog, the New York measles epidemic was linked to a 14-year-old boy who carried the measles virus from Israel into a Hasidic Jewish community. To help stave off further measles cases, in June 2019, New York eliminated religious exemptions for required vaccines, like MMR (measles, mumps, and rubella). Subsequent investigations have implicated Ukraine as the potential initial source of the New York outbreaks. Ukraine is struggling with a measles epidemic that has infected more than 58,000 people in 2019 alone. Some visitors to the U.S. came from communities in Israel where many people make an annual pilgrimage to the grave of a revered rabbi in the former Soviet Union state.

In Ukraine, only half the population believes vaccines are effective, compared with 84% in the U.S. Underlying their disbelief in vaccine safety and efficacy is a deep mistrust of government authorities and a desire for fierce independence, despite the increased risk posed by unvaccinated people. As was highlighted in the September 6th blog, this condition, called vaccine hesitancy, is now actually considered a disease. It is even recognized by the WHO as one of the ten biggest health threats in the world. Misinformation about the dangers of vaccines continues to be promulgated by notorious personalities and is widely spread by social media websites. Sadly, it appears that stopping the epidemic of vaccine hesitancy is an even bigger challenge than putting an end to measles.

But there is a second reason to eliminate measles, a disease that kills more than 130,000 people globally per year. Measles was the first disease recognized to increase susceptibility to other infections with many of the measles-related deaths from pneumonia or diarrhea caused by other infectious agents. That this increased risk of other infections is caused by immunosuppressive effects of the measles virus was first recognized in the 19th century. But the mechanism behind the immunosuppression wasn’t all that clear until November 1st of this year.

During a 2013 outbreak of measles involving 77 unvaccinated Dutch children living in an Orthodox Protestant community, two research groups followed the impact of measles on various aspects of these children’s’ immune systems. On November 1st, 2019, the results of both studies were reported.

In one study, published in Science, a blood assay called VirScan was used to track antibodies to thousands of components of different human pathogens. The researchers found that measles caused the elimination of on average about 20% of their antibody repertoire to a whole host of viruses. And some children experienced a 70% decline in antibodies to other pathogens. Notably, these effects on the immune system weren’t observed in infants that had been vaccinated with MMR. They concluded that the reduction in this aspect of immunity (humoral immune memory) by measles is responsible for the potential vulnerability to future infections.

In the second study, which was published in Science Immunology, the researchers went right to the source of antibodies: B memory cells, which “remember” past infections. They found that measles-induced amnesia is related to the killing of B cells that target other pathogens.

The results of these studies on how the measles virus compromises immunity, thereby generating potential vulnerability to future infections, underscore the need for widespread vaccination. They also provide additional impetus to conquer the disease called vaccine hesitancy.