Over the last decade, evidence has mounted that the measles vaccine protects in not one but two ways: Not only does it prevent the well-known acute illness that frequently sends children to the hospital, but it also appears to protect the body from other infections over the long term.
How does this work?
Reporting on Oct. 31 in Science, an international team of researchers led by investigators at the Brigham and Harvard Medical School show that the measles virus wipes out 11 percent to 73 percent of the different antibodies that protect against other viral and bacterial strains a person was previously immune to — anything from influenza to herpes virus to bacteria that cause pneumonia and skin infections.
The study is the first to measure the immune damage caused by the virus and underscores the value of preventing measles infection through vaccination, the authors said.
“The threat measles poses to people is much greater than we previously imagined,” said senior author Stephen Elledge, PhD, the Gregor Mendel Professor of Genetics and of Medicine in the Blavatnik Institute at HMS and the Brigham. “We now understand the mechanism is a prolonged danger due to erasure of the immune memory, demonstrating that the measles vaccine is of even greater benefit than we knew.”
Elledge and colleagues found that those who survive measles gradually regain their previous immunity to other viruses and bacteria as they get re-exposed to them. But because this process may take months to years, people remain vulnerable in the meantime to serious complications of those infections.
As a result, researchers say clinicians may want to consider strengthening the immunity of patients recovering from measles with a round of booster shots of all routine vaccines, such as hepatitis and polio.
Answers in the Blood
This new discovery was made possible thanks to VirScan, a tool Elledge, George Xu and Tomasz Kula, doctorate students in the Elledge Lab, developed in 2015. VirScan detects antiviral and antibacterial antibodies in the blood that result from current or past encounters with viruses and bacteria, giving an overall snapshot of the immune system.
For the study, Elledge’s group used VirScan to measure antibodies before and two months after infection in blood samples from unvaccinated children who’d contracted the disease during a 2013 measles outbreak in the Netherlands. The researchers also compared the measurements to uninfected children and adults.
When Kula examined an initial set of these samples, he found a striking drop in antibodies from other pathogens in the measles-infected children that “clearly suggested a direct effect on the immune system,” the authors said. This was strong support for the immune-amnesia hypothesis previously put forward in 2015 from epidemiological data by Michael Mina, MD, PhD, who helped initiate the new study while serving as a postdoctoral researcher in Elledge’s lab. Mina, first author of the recent Science paper, is now an assistant professor of epidemiology at the Harvard T.H. Chan School for Public Health.
Further tests revealed that a severe measles infection reduced people’s overall immunity more than a mild case of measles. This could be particularly problematic for certain categories of children and adults, the researchers said, especially those who are malnourished or less healthy before contracting the virus.
Inoculation with the MMR (measles, mumps, rubella) vaccine did not impair children’s overall immunity. This aligns with decades of research.
Ensuring widespread vaccination against measles would not only help prevent the 120,000 deaths that will be directly attributed to measles this year alone but could also avert potentially hundreds of thousands of additional deaths attributable to the lasting damage to the immune system, the authors said.
“This drives home the importance of understanding and preventing the long-term effects of measles, including stealth effects that have flown under the radar of doctors and parents,” Mina said. “If your child gets the measles and then gets pneumonia two years later, you wouldn’t necessarily tie the two together. The symptoms of measles itself may be only the tip of the iceberg.”