Measles pose “immune amnesia” threat

Two international studies will give local authorities more reasons to step up their fight to end the measles epidemic in Samoa.

The studies published in two Science journals, Science and Science Immunology on Friday,  found that measles can cause “immune amnesia” in its victims, leaving them defenceless to illnesses they have fought before.

They also reveal new information about a disease that has made a deadly global resurgence - including in Samoa where there is currently an outbreak.

As of last week, measles has infected 15 people in Samoa, with 314  suspected cases. 

Three deaths, that of a 14-month-old, an eight-month-old and a 37-year-old are being treated as measles-related. 

“Measles really compromises the whole immune system,” Dr. Helen Petousis-Harris, a Vaccinologist and Senior Lecturer from the University of Auckland told the Samoa Observer.

“Even once you have gotten rid of the virus you can be significantly immune compromised for up to five years after having the infection.”

The papers independently studied unvaccinated children’s immune systems before and after being infected with measles.

They both found that the measles infection “eliminates a large proportion of protective antibodies in humans, leaving them more vulnerable to other infections,” Professor Michael Baker from the University of Otago told the Science Media Centre in New Zealand. 

“These studies add to the increasing epidemiological evidence around the non-specific beneficial effects of vaccines.”

The studies prove wrong the myth that recovering from measles makes one stronger against it, and other illnesses, Dr. Petousis Harris said.

“Measles virus infects some of the most important cells of the immune system and during its stay wreaks havoc. In just a few days it can infect up to 70 per cent of important immune memory cells. 

“Importantly, measles virus replaces immune memory cells (immunity you had already established) with new measles-immune memory cells. Ironically, the immune memory made against measles is fantastic but the host has an increased vulnerability to other pathogens.”

She explained that even in unvaccinated children who had mild measles infections, 20 per cent of their antibodies were eliminated, while those with severe infections lost 73 per cent.

“Only once the children became re-exposed to the bugs they had previously become immune to did their immunity regenerate.”

Even today, during New Zealand’s rampant measles epidemic with nearly 2000 cases in 2019, Dr. Petousis-Harris saw social media posts with parents excited to have their children’s immune system strengthened by their exposure to measles.

“Obviously this is not the case. The risks of not vaccinating against measles have never been clearer, several people almost lost their lives this year because of measles, and two unborn babies died (in New Zealand),” Dr. Petousis-Harris said.

Dr. Nikki Turner, chair of the Immunisation working group to the Strategic Advisory Group of Experts (S.A.G.E.) to the World Health Organistion (W.H.O.) said that from a public heath perspective, these studies show the consequences of measles are probably underestimated.

“It is likely that the reduction in morbidity and mortality from the effects are even greater than direct effects,” she told the Science Media Centre.

“So when the W.H.O. reports that measles vaccination averted more than 21 million deaths from 2000 to 2017, we could possibly even double that amount if we count the indirect effects.”

She said the way public health programmes currently encourage people to vaccinate their children (or themselves, if they missed out on childhood vaccine programs) is to tell people they can avoid getting measles, but the lesson that their immune system could be saved should be shared.

The vaccine itself protects against the “immune amnesia” the virus causes, as well as the symptoms of measles itself.

“However, the reasons for why people choose to decline measles vaccination are likely to be more around lack of trust in the science, scientists, health authorities and policy makers, not lack of evidence,” Dr. Turner added.

The studies, “Incomplete genetic reconstitution of B cell pools contributes to prolonged immunosuppression after measles” and “Measles virus infection diminishes preexisting antibodies that offer protection from other pathogens” are available to read online at sciencemag.org. 

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