Children not vaccinated against measles are more likely to die from other illnesses, warns a new study.
Infection with the virus increases the risk of other life threatening conditions in the next two to three years, according to the findings.
Youngsters may catch other bugs which they previously developed immunity to – which was erased by measles.
It mainly spreads through memory cells – resulting in a phenomenon called immune-amnesia.
The immune system cannot remember some of the diseases it has fought in the past – exposing children to re-infection.
The US team’s findings explain the mysterious large drops in mortality of up to 50% following the introduction of measles vaccinations.
Prior to vaccines, measles was usually associated with much less than half of childhood deaths. That went unnoticed in previous years because clinicians would not, for example, link a death from another disease back to a measles infection.
The child may have had it two years earlier – and that wiped away the immune memory for the other infecting pathogen.
Dr Michael Mina, an expert in communicable diseases at Harvard Medical School, said: “Prior to vaccination, measles infected nearly everyone.
“Because we now think that measles infections may erase pre-existing immune memory, by preventing measles infection through vaccination, we prevent future infection with other infectious diseases allowed back into the body by the damage done by measles.
“The epidemiological data from the UK, USA and Denmark shows that measles causes children to be at a heightened risk of infectious disease mortality from other non-measles infections for approximately 2-3 years.”
Up to a quarter of young children are not vaccinated against measles in some parts of the UK, official figures show.
Last month Public Health England (PHE) urged parents to book jabs before children return to school, amid warnings that Britain has lost its ‘measles-free’ status.
Many outbreaks were being fueled by visits to European countries over the summer holidays.
Dr Mina said: “Prior to vaccination, the incidence of measles from year to year could explain almost all of the variation in non-measles infectious disease deaths that occurred over multiple decades.
“Altogether, this suggests that measles may have been associated with as much as half of all childhood deaths due to infectious diseases prior to vaccination, and thus explaining the mysterious large drops in mortality seen following introduction of the vaccine.”
He added: “It may be that the only way for a child to recover from this immune-amnesia is if their memory cells ‘relearn’ how to recognise and defend against diseases they had known before, and they can do this through re-exposure to the pathogen or by re-vaccination against that particular infection.”
Dr Mina says the most urgent problem is the resurgence of measles. But the risks extend far beyond one specific vaccine, he told a meeting of the European Society of Clinical Microbiology and Infectious Diseases in Bilbao, Spain.
Measles is a serious, highly contagious disease causing fever, rash and other symptoms in most children. Complications include pneumonia and brain inflammation.
Last year it killed about 1 in every 75 children infected with the virus, leading to more than 100,000 deaths.
But it is this re-exposure to the other pathogens that pose the long-term risks following a measles infection.
A recent epidemiological study, led by Dr Rik de Swart of the Department of Virosciences at Erasmus Medical Centre, Rotterdam, looked at more than2,000 children infected with measles in the UK.
They were significantly more likely to require physician visits and had higher rates of antibiotic prescriptions for two to five years afterwards.
Dr Mina said: “It might be reasonable to consider re-vaccination with other childhood vaccines following measles infection.”
But he pointed out many children with measles generally have not been vaccinated, whether because of parental refusal or the lack of access to vaccinations in the first place, so this “may not always be a viable option.”
A large measles epidemic has swept Europe in the past three years, with 47,690 cases reported between 1 January 2016 and 30 June 2019.
Only eight countries – Romania (14,712 cases), Italy (10,439), France (5,812), Greece (3,288 ), United Kingdom (2,412), Germany (2,240), Poland (1,874) and Bulgaria (1,295) – were responsible for 88 per cent of the cases.
Britain was declared “measles free” by the World Health Organisation (WHO) in 2016 after a 36-month period with no “endemic” transmission – meaning the only outbreaks in that time had started abroad.
Since 2016, however, uptake of the MMR jab has fallen each year and WHO has now revoked the country’s measles-free status.