Vaccination stimulates an immune response to a particular virus or infection. When unvaccinated people live in an area filled with vaccinated folk, in other words, a herd of vaccinated people, they may be protected by what is called the herd effect – since everyone else is vaccinated, they won’t get sick. Since they can’t get the infection, they protect the unvaccinated from infection with a ‘buffer’ of safety.
However, this happens only when there are enough vaccinated people, otherwise the protection cannot reach those outside the protected arena. Due to this shortfall, all vaccinated people cannot protect the unvaccinated from a specific disease. This is herd immunity failure.
Herd Immunity Failure: Recent Examples
Previously, school children in the modern societies who weren’t vaccinated were been protected by the majority of children who were vaccinated. Parents then had a false sense of security, believing they didn’t have to vaccinate their children because the disease threat is modified or nonexistent. Parents may also have chosen not to vaccinate for religious reasons or misconceptions about vaccine safety. Unfortunately, the perception of safety has caused a resurgence of pertussis and measles along with other epidemics. The “herd” couldn’t protect the population.
Although studies do not link the standard DTaP (diptheria, tetanus,a cellular pertussis) with autism, many parents continue to withhold or delay the vaccine. Previous herd protection began to fail as the numbers of increased non vaccinated children grew and whooping cough made a frightening come back. While whooping cough is an exhaustive cough in adults, it taxes the immature respiratory system of children and can be deadly: 2010 had over 27000 cases of pertussis in US alone, and 2012 saw the highest number of cases since the vaccine was introduced – 41,000 cases.
One solution has been mass vaccination of pregnant women with the Tdap vaccine and to vaccinate all potential grandparents and others who would be around the vulnerable newborn. Until re-vaccination reaches a large percent of the population, children and infants are no longer protected by the herd. Vaccinating those around the vulnerable infant creates a buffer zone by protecting the infant from family members. Eventually, as more people are vaccinated, the circle of herd protection grows.