New research explains the link between the introduction of the measles vaccine and an overall drop in child mortality
Half a century ago, measles vaccines were introduced in the United States. What followed was an impressive decrease in child mortality – and not just from the measles. Childhood deaths from a whole array of infectious illnesses declined. This trend repeated itself in other regions as well. When the measles vaccine was introduced, overall childhood mortality rapidly decreased.
The reason for this striking correlation has always been something of a mystery. While it might be supposed that the decline in mortality would be related to the likelihood that vaccinated children have greater overall access to health services, research into the matter has revealed that there is more going on. Research detailed in an article published last Thursday in the journal Science has given a bit more insight into the interesting phenomenon.
Michael Mina, a member of the team of researchers, told NPR that they had been intrigued by the correlation, stating that, “it’s really been a mystery — why do children stop dying at such high rates from all these different infections following introduction of the measles vaccine”. The inquiry led them to an answer: they “found measles predisposes children to all other infectious diseases for up to a few years”.
Mina and his colleagues took a look at national data from the United States, England, Wales and Denmark, searching for an explanation. The reason for this predisposition, it seems, is that the measles virus suppresses the immune system’s “memory”. That is to say, it prevents the immune system from “remembering” the infections which it has already fought off. So, whereas a normal person would not be susceptible to the particular strain of an illness which their body has already beaten, someone who has contracted the measles in the intervening time must regain that immunity, falling ill a second time.
According to the World Health Organization, measles remains one of the leading causes of death among children worldwide, in spite of the availability of a safe, cost-effective vaccine. In 2013, the WHO estimates that approximately 84% of children received the measles vaccine by their first birthday. Yet in the same year, there were 145,700 deaths from the disease globally, most of these children under the age of 5. It would be difficult to calculate how many non-measles deaths were caused by the reduced immunity that the virus confers, but the number is likely considerable. As reported by Science, mass measles vaccination has been shown to “reduce overall childhood mortality by 30 to 50% in resource-poor countries, and by up to 90% in the most impoverished populations”.
This new information adds another level of urgency to the push for measles vaccination, which has been in the news over the past few years following a number of major measles outbreaks and resurgences in unvaccinated communities worldwide. As the Science article explains, “Even where control has been successful, vaccine hesitancy threatens the gains that have been made”.
Unsubstantiated claims of a link between vaccination and autism, brought to the public eye by celebrity figures like actress Jenny McCarthy, have caused many parents to refuse measles-mumps-rubella (MMR) immunization for their children. Numerous scientific studies have since demonstrated that there is no link between the MMR vaccine and autism, but the rumor mills have already cost many children life-saving immunity.
The World Health Organization’s Global Measles and Rubella Strategic Plan aims to reduce global measles deaths by at least 95% (compared with 2000 levels) by the end of 2015.