Measles vaccines could protect children against more than just a single disease, a new study concludes.
Researchers examined medical records from the United States, Denmark, England and Wales just before and after the introduction of measles vaccines in those nations. They found a significant decrease in the number of childhood deaths from infectious diseases in the two to three years following the start of immunization programs.
"With mathematical analysis of all of the epidemiological evidence we have, it seems that when measles was prevalent, it would go through a population, and that population would be at increased risk for mortality from other diseases for about 28 months, and in proportion to how many people were infected with measles," Michael J. Mina, formerly a postdoctoral student at Princeton, said.
Measles also appears to significantly reduce the ability of the human body to respond to other diseases. The illness appears to greatly deplete B and T lymphocytes. These serve to record the presence of diseases, providing immunity against future infections. When measles strikes, the immune system eventually learns to fight against the illness but can lose the ability to fight off other microorganisms for a period of time. This can leave children susceptible to a wide range of other diseases, and they may need to become infected again with illnesses to regain immunity.
Measles vaccines are able to protect children against that disease without reducing B and T lymphocytes, potentially protecting resistance against other illnesses as well.
Analysis of the data originally showed only a weak statistical correlation between measles vaccinations and childhood deaths from infectious diseases. Once they changed the amount of time that immune systems were subject to "amnesia," a correlation became clear.
"In other words, reducing measles incidence appears to cause a drop in deaths from other infectious diseases due to indirect effects of measles infection on the human immune system," said Bryan Grenfell of Princeton University.
Medical researchers believe that measles may have contributed to as many as half of all deaths among children in the industrialized world when the disease ran rampant.
Future research will examine a large group of people over a period of time to explore how the vaccine against measles could protect children against other potentially fatal infectious diseases.
"And we need to explore consequences for resource-poor countries, where measles causes much more immediate mortality," Mina stated in a university press release.
Analysis of the apparent correlation between deadly childhood infections and the measles vaccine was detailed in the journal Science.
Photo: Paho | WHO | Flickr
