New research shows that measles wipes out between 20 and 50 percent of antibodies against an array of bacteria and virus, depleting a child’s previous immunity.
The study shows that a measles-ravaged immune system must relearn how to protect the body against infections. It details the scope and mechanism of this measles-induced immune amnesia and underscores the importance of measles vaccination. It suggests that those infected with measles may benefit from booster shots of all previous childhood vaccines.
Over a decade ago, evidence has shown that the measles vaccine protects in not just one way: it prevents measles that frequently send kids to the hospital and also appears to protect children from other infections over the long term.
How does it work?
Many researchers have suggested that the vaccine provides a general boost to the immune system.
Other researchers have also hypothesized that the extended productive effects of the vaccine stem from preventing measles infection itself. According to the theory, the virus can impair the immune memory of the body, causing so-called immune amnesia.
The vaccine doesn’t only prevent measles, but also prevent the body from forgetting or losing its immune memory and preserves its resistance to other infections.
Previous research hinted at the effects of immune amnesia, showing that suppression of immune could last for two to three years.
However, several scientists have continued to debate which hypothesis is actually correct. One of the questions begging for answer is: if immune amnesia is real, how does it happen and how severe is it.
Thankfully, a study carried out by international team of researchers led by investigators at Harvard Medical School, Brigham and Women’s Hospital and the Harvard T.H. Chan School of Public Health gives us the much-needed answers.
The researchers found that the measles virus wipes out 1% to 73% of the different antibodies protecting the body against bacterial and viral strains a person was previously immune to – from influenza to herpes virus to bacteria that cause skin infections and pneumonia.
It means, if a person had 100 antibodies against chicken pox before contracting measles, such person may get that number reduced to just 50 after emerging from measles, cutting their chicken pox protection in half. In fact, the protection could be lower if some of the antibodies lost are potent defences called neutralizing antibodies.
The author says, “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 senior author Stephen Elledge says, “The threat posed by measles to people is greater than we previously imagined.” “We now understand the mechanism is a prolonged danger because of the erasure of the immune memory, demonstrating that the measles vaccine provides greater benefits than we knew.”
The discovery that measles depletes people’s antibody repertoires, partially obliterating immune memory to most previously encountered pathogens, supports the immune amnesia hypothesis.
Mina added “This is the best evidence yet that immune amnesia exists and impacts our bona fide long-term immune memory.”
Mina, Elledge and colleagues discovered that those who survive measles gradually regain their previous immunity to other bacteria and viruses as they get re-exposed to them. But because the process of recovering may take months or years, people may remain vulnerable in the meantime to serious complications of those infections.
The author says, “Revaccination following measles could help to mitigate long-term suffering that might occur from immune amnesia and the increase susceptibility to other infections.”
Two steps forward, one step backward
Measles is one of the most contagious diseases and it infects over 7 million people and kills over 100,000 people every year around the world, reports the WHO. In early 2019, the cases are on the rise. In the U.S., people who get infected with measles require hospitalization, CDC says. Some infected people experience well-known long-term consequences such as hearing loss, vision loss and brain damage.
Answer in the blood
VirScan detects bacterial and antiviral antibodies in the blood that result from past or current encounter with bacteria and viruses, giving an overall snapshot of the immune system.
During a 2013 measles outbreak in the Netherland, study co-author Rik de Swart had gathered blood samples from children that were not vaccinated. For the new study, Elledge group used VirScan to measure antibodies before and 2 months after infection in 77 children from de Swart’s samples who had contracted the disease. The researchers compared the measurements to those of 115 unaffected adults and children.
When Kula examined the initial set of these samples, he discovered a striking drop in antibodies from other pathogens in the measles-infected children that “suggested a direct effect on the immune system,” said the author.
Elledge says, “This proved to be the first definitive evidence that measles affect the levels of protective antibodies, providing a mechanism supporting immune amnesia.”
The authors stress that the effects discovered in the current study occurred in previously healthy children. Because measles is known to hit malnourished children harder, the degree of immune amnesia and its effect could be even more severe in less healthy populations.
Elledge says, “The average child might emerge from measles with a dent in their immune system and their body will be able to handle it.” “But kids on the edge – such as those with severe immune deficiencies or measles infection or those who are malnourished – will be in serious problem.”
The research found that inoculation with the measles, mumps, rubella (MMR) vaccine did not impair children’s overall immunity. The results align with decades of research.
The authors says, “Ensuring widespread vaccination against measles would not just help prevent the 120, 000 deaths that will be attributed directly to measles this year only but could also help avert potential hundreds of thousands of death attributed to the lasting damage to immune system.”
Mina says, “This shows the importance of understanding and preventing the long-term effects of measles, including stealth effects that have flown under the radar of parents and doctors.’’ “If your kid gets the measles and then gets pneumonia 2 years later, you would not necessarily tie the two together. Measles symptoms may be the only tip of the iceberg.”