MEASLES CAN CAUSE long-term damage to the immune system – resetting it to a baby-like state and leaving people vulnerable to other infections, scientists have said.

According to new research, the measles virus deletes part of the immune system’s memory, removing previous immunity to other infections in both humans and ferrets.

Research from the Wellcome Sanger Institute, University of Amsterdam and their collaborators showed that the disease resets the human immune system to an immature state with only limited ability to respond to new infections.

Published in the journal Science Immunology, the study explains why children often catch other infectious diseases after measles.

Scientists said the research has great implications for public health, as falling vaccination rates are resulting in rising cases of measles.

They said this in turn could cause an increase in cases of other dangerous infections such as flu, diphtheria or tuberculosis, even in people who were previously immune.

Dr Velislava Petrova, lead author from the Wellcome Sanger Institute and Cambridge University, said: “This study is a direct demonstration in humans of ‘immunological amnesia’, where the immune system forgets how to respond to infections encountered before.

“We show that measles directly causes the loss of protection to other infectious diseases.”

The study

To see what measles does to the immune system, researchers looked at a group of unvaccinated people in the Netherlands.

They took blood samples from healthy volunteers, who were followed up from repeat sampling after a measles outbreak in 2013.

The researchers sequenced antibody genes from 26 children both before and 40-50 days after their measles infection.

Specific immune memory cells that had been built up against other diseases, and were present before the measles virus infection, had disappeared from the children’s blood, scientists found.

This “immunological amnesia” was then tested in ferrets, showing that infection with a measles-like virus reduced the level of flu antibodies in the animals that had been previously vaccinated against flu.

Researchers also found that the measles virus resets the immune system to an immature state which can only make a limited repertoire of antibodies against disease.

Professor Colin Russell, senior author from the University of Amsterdam, said: “For the first time we see that measles resets the immune system and it becomes more baby-like, limiting how well it can respond to new infections.

“In some children the effect is so strong it is similar to being given powerful immunosuppressive drugs.

“Our study has huge implications for vaccination and public health as we show that not only does measles vaccination protect people from measles, but also protects from other infectious diseases.”

Second study

In a separate study published in the Science journal, researchers used a tool called VirScan to analyse the responses of antibodies in 77 unvaccinated children aged four to 17 before and after measles infection.

The technology tracks antibodies to thousands of viral and microbial antigens in the blood.

Led by investigators at Harvard Medical School, Brigham and Women’s Hospital and the Harvard TH Chan School of Public Health, scientists found the disease wiped out 11% to 73% of the antibody repertoire across individuals two months after measles infection.

Professor Michael Mina said: “Imagine that your immunity against pathogens is like carrying around a book of photographs of criminals, and someone punched a bunch of holes in it.

“It would then be much harder to recognise that criminal if you saw them, especially if the holes are punched over important features for recognition, like the eyes or mouth.”

Professor Mina and colleagues found those who survive measles gradually regain their previous immunity to other viruses and bacteria as they get re-exposed to them.

However, because this process may take months to years, people remain vulnerable in the meantime to serious complications of those infections.

Vaccination

In the late 1960s a highly effective measles vaccine was introduced in the UK, and in 2017 the disease had been completely eliminated from the country.

However, measles is highly contagious and cases are rising again, with the UK’s vaccination uptake dropping below the required level of 95% of the population.

This led to the UK losing its World Health Organisation (WHO) measles elimination status in August.

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In recent months, concerns have been raised about the possibility of Ireland losing its measles-free status given the recent spike in cases here.

The WHO defines measles elimination as the absence of the illness circulating, high vaccine coverage, and a robust process to identify cases.

In the first quarter of 2019, there were 231 confirmed cases of measles in England and Wales. There were 991 confirmed cases last year, a jump from 284 cases in 2017. Most cases are linked to travel in Europe, where many countries have experienced measles outbreaks. 

Ireland has also seen an increase in cases in recent years. The number of cases here tripled from 25 in 2017 to 77 in 2018.

There have been 56 reported cases to date in 2019 – 33 of which have been confirmed.

Most cases in Ireland to date this year were among children, however there were 17 cases among people aged 20-44. Thirty-one cases involved males and 25 cases related to females. 

In Ireland, all children are entitled to, and advised to, get the MMR vaccine at the age of 12 months. They are supposed to get a second dose when four or five (in junior infants). Adults who are not sure if they received the vaccine as a child are advised to contact their GP to check and discuss getting a booster if needed. 

The uptake rate for the MMR vaccine in Ireland is 90.1% – below the HSE’s goal of 95%,  the level needed for herd immunity. 

TheJournal.ie explored the issue in a previous episode of The Explainer podcast:

The Explainer / SoundCloud

MEASLES: WHAT YOU NEED TO KNOW

How to recognise the symptoms?

• High fever
• Cough
• Runny nose
• Red eyes
• Red rash that starts on the head and spreads down the body – this normally starts a few days after onset of illness; the rash consists of flat red or brown blotches, which can flow into each other; it lasts about four to seven days
• Vomiting, diarrhoea and tummy pain may also happen

Measles can cause chest infections, fits (seizures), ear infections, swelling of the brain and/or damage to the brain.

The Department of Health gives the following advice in relation to the MMR vaccine:

• All children should get the MMR vaccine when they are aged 12 months; if any child aged over 12 months has missed this vaccine they should get it now from their GP
• All children should get a second dose of MMR vaccine when they are four to five years old or in junior infants at school; if any child in senior infants or older has missed this vaccine they should get it now from their GP
• Adults under 40 years who have not had measles or have not received two doses of MMR vaccine should contact their GP to get the MMR vaccine
• Adults over 40 years of age may sometimes be at risk and if such adults never had measles nor a measles-containing vaccine they should consider getting the MMR vaccine from their GP

What advice does the HSE give to people who think they might have measles?

• Do not go to work, school or crèche
• Stay at home and phone your GP – tell the doctor or nurse that you think you might have measles
• Stop visitors coming to your home
• Pregnant women who have been exposed to measles should seek medical advice as soon as possible

With reporting by Hayley Halpin