Herd immunity is a term that conjures up for me a heart-warming picture of animals protecting each other through the safety that comes with greater numbers.
However, the hard reality in much of the animal kingdom is that many herds place their weak or sick members on the outskirts. This makes them easy targets for predators, keeping the herd as a whole faster and stronger as the vulnerable are picked off.
Fortunately, herd immunity for human beings doesn't work like that. The goal here is to protect the weak by creating a buffer between them and any danger. In this scenario, the danger is disease and the buffer is immunization.
The aim of herd immunity is to deflect the ravages of sickness from the individual and the community. When an individual is vaccinated, it is meant for their protection and also as protection for the community.
People who have not been vaccinated will be safer because the risk of catching a disease is lessened. If enough people are impervious to a disease, that disease may eventually disappear simply because there are no hosts to carry it.
According to wisegeek.com, herd immunity may be possible in some instances when only 50 percent of a community is vaccinated against a particular disease. In less ideal situations, it may take vaccinations in 90 percent of the community to achieve herd immunity.
While the goal is protection of the individual and the community, actual performance does not always fill the bill. As the Discovery Fit and Health website pointed out, herd immunity isn't a perfect stratagem. Things can go wrong.
Vaccines don't always offer complete protection and people can still get sick. Some vaccines only offer protection for a few years.
If enough people have their immunity wear off around the same time, outbreaks of disease are a possibility. Sometimes people have adverse side effects.
In recent years, fewer parents are getting their children vaccinated, because of concerns about these possible side effects. Even so, the majority of children are still being vaccinated and herd immunity, by and large, is still in play. Immunizations against various diseases amongst the general population can protect others who have not been vaccinated.
The National Institute of Allergy and Infectious Diseases website reminds that some people can't handle vaccinations. Small babies, pregnant women, people who are ill or have weakened immune systems or allergies, according to the herd immunity paradigm, may be safer because they are less likely to ever come in contact with the disease.
Resources:
What is Herd Immunity?
http://www.wisegeek.com/what-is-herd-immunity.htm
Community Immunity ("Herd" Immunity)
http://www.niaid.nih.gov/topics/pages/communityimmunity.aspx
What is herd immunity?
http://health.howstuffworks.com/diseases-conditions/infectious/herd-immunity2.htm
Reviewed June 20, 2011
Edited by Alison Stanton
Visit Jody's website and blog at http://www.ncubator.ca and http://ncubator.ca/blogger