Measles causes 'immune amnesia' leaving us vulnerable to other diseases

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Measles infections can wipe out a child's immune system for up to five years - resetting it to a baby-like state, a study suggests.

When the measles vaccine first became available in the 1960s, something curious happened: Scientists began to notice a drastic drop in the number of children dying from other infectious diseases as well.

'When people get an infection, their immune system creates antibodies to fight it off'.

Analysis of blood from 77 unvaccinated Dutch children found that the virus eliminated between 11% and 73% of their antibodies, Elledge's team found. Antibodies are the cells that remember past encounters with pathogens and help the body avoid repeat infections.

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

New Zealand experts say these findings, published in Science Immunology and Science journals, emphasise the importance of widespread vaccination.

However researchers have now discovered measles "resets" the immune system, wiping out the immunity children have developed to other illnesses, effectively leaving them with the same scant protection they had as newborns.

In addition, the 20% of children most affected by measles lost over half of their pathogen-specific antibodies to most pathogens, and in some children, up to 70% antibody loss against specific pathogens was detected, the researchers noted. "But kids on the edge-such as those with severe measles infection or immune deficiencies or those who are malnourished-will be in serious trouble".

He recommended that people vaccinated against other diseases who contract the measles should consider getting another round of shots.

"We showed that measles-like viruses can delete pre-existing flu immune memory from ferrets", explains Professor Paul Kellam, from the Department of Infectious Disease at Imperial and previously from the Wellcome Sanger Institute.

Scientists say measles selectively and exclusively infects humans.

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The Science paper looked at the diversity of antibodies in the bloodstream using a new technique called VirScan.

For people vaccinated decades ago, the amount of measles antibodies in the blood might be too low for VirScan to spot. All children have immune cells which have learned to recognise viruses and bacteria, from pneumonia to TB, whether they have come across them or been vaccinated with traces of them.

They're then more vulnerable to other bacterial and viral infections - even those they've already been vaccinated against or have had before.

What's more, this vulnerability can last for months on end, maybe even years.

"I think the main message is clear: Protecting children from measles infection via vaccination is incredibly important, both because of the direct results of the pathogen and its long-term consequences on immune memory", Metcalf says. Trillions of antibodies can be found in every 3 ounces (1 microliter) of blood, Mina said.

The measles vaccine does far more than keep one disease at bay. Nikolai Petrovsky, from Australia's Flinders University, suggests this research should entirely put to bed misinformation from certain sectors of the community that result in absurd "pox parties" where parents expose children to measles in the hopes of improving the child's immune response.

After measles infection, the collection of antibodies kids had built up over their lifetime shrank - sometimes drastically.

"What we were actually witnessing was [the] reeducation" of their immune system, Mina said.

"You have this really rapid [antibody] decline with measles, and then a slow increase", he said.

The research, published in Science Immunology, also has implications for public health, as falling vaccination rates and resulting in rising cases of measles, which could also cause an increase in cases of other risky infections such as flu, diphtheria or tuberculosis, even in people who were previously immune.

Furthermore, 'the children who received the MMR vaccine showed no reduction in these antibodies'.

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