Measles is more harmful than previously suspected, scientists say.

Two separate studies of 77 unvaccinated Dutch children have revealed that it can cripple immunity against viruses and bacteria for the long term, creating an “amnesia” that leaves people more vulnerable to infections by other pathogens.

“We’ve found really strong evidence that the measles virus is actually destroying the immune system,” says Stephen Elledge, from the Howard Hughes Medical Institute, US, a co-author of a study published in the journal Science.

In that study, led by Michael Mina from Brigham and Women’s Hospital in the US, the researchers used a tool called VirScan to analyse the responses of antibodies in the children before and after contracting measles.

They found that the disease wiped out between 11% and 73% of the antibody repertoire across individuals two months after infection, severely compromising immune memory of various infectious agents even after recovery. {%recommended 8703%}

Antibody depletion was not observed in infants vaccinated against measles, mumps and rubella.

In the other study, published in Science Immunology, a team led by Velislava Petrova, from Wellcome Sanger Institute, UK, sequenced antibodies produced by B cells (one of the primary immune cells able to recognise and respond to a virus) from the 77 children.

They identified two indications of immune suppression: incomplete restocking of the B cell pool and compromised immune memory due to depletion of B cell clones.

In additional animal studies, they found measles-infected ferrets already vaccinated against the flu became less immune to the virus and experienced more severe symptoms upon secondary flu infection.

“This work highlights the importance of MeV [measles] vaccination not only for the control of measles but also for the maintenance of herd immunity to other pathogens, which can be compromised after MeV infection,” they write.

Measles is very contagious and before the development of a vaccine in 1963 there were three to four million cases a year in the US alone. That fell to just 86 in 2000, when the disease was declared eliminated, but numbers are climbing again. The US Centres for Disease Control has reported more than 1250 cases so far this year.