Despite what you think is happening when you read antivaccination blogs, most people in the developed world vaccinate their children. And in the relatively undeveloped world, they are demanding more vaccines so that their children will live longer. In the USA alone, far less than 1% of children, 19-35 months, are completely unvaccinated. The problem, at least in the USA, is that those unvaccinated children tend to be clustered in small geographical areas where individuals who share the typical characteristics of many vaccine deniers tend to live.
The complication is that the herd immunity can break down rather quickly when the vaccination uptake drops below 80-90% in these clusters. And all it takes is one person carrying a vaccine preventable disease from an area, where it is endemic, to then start an outbreak or epidemic very quickly in one of these low vaccine uptake clusters. For a disease like measles, which is very contagious, it jumps from an infected person to unvaccinated individuals quite rapidly, sometimes before public health authorities can contain it. Measles is easily prevented with the MMRV vaccine (which also protects children against mumps, rubella, and chickenpox).
In a recent article published in Pediatrics, researchers investigated a measles outbreak in Minnesota in 2011. The authors, lead by Pamala Gahr of the Minnesota Department of Health, determined that the outbreak began when an unvaccinated 2-year-old travelled to Kenya, where he contracted the measles virus. Upon returning to the United States, the child developed a fever, cough and vomiting, some of the early signs and symptoms of measles. Unfortunately, prior to a diagnosis of measles, the child passed the virus on to three children in a child day-care center and another household member. The measles then spread from individual to individual within a low vaccine uptake area, a Somali immigrant community in the Minneapolis area. Eventually, more than 3,000 people were exposed to the disease. Continue reading “One unvaccinated child was patient zero of a measles epidemic”