Most of the parenting decisions I have made are none of your business. Did I breastfeed or bottle feed my children? Did I Ferberize them or sleep next to them in my bed? Did I stay home with them or maintain my career and send them to day care? I'm not telling you because these are personal decisions which will have no effect on your life or the lives of your children.
The decision to vaccinate my children, however, is not personal. It is a matter of public health. And I have the right to know that my neighbors, and that you, are vaccinating. The answer about why I do care hinges on the concept of herd immunity.
Do not be fooled by herd immunity naysayers. Doctors noticed the benefits of having a large population immune to certain diseases during the smallpox outbreaks in the nineteenth century. 150 years ago, doctors noted that in communties where a large percentage of the population had either been innoculated or had contracted smallpox, the virus could not make inroads and did not effect the susceptible remainders of the community. (See Fine P (1993). "Herd immunity: history, theory, practice". Epidemiol Rev 15 (2): 265–302.) In the mid-twentieth century, public health officials used herd immunity to eradicate smallpox from the planet.
Herd immunity functions properly when enough of us are vaccinated to hinder the introduction of certain diseases into our communities. For example, polio has been absent from the United States since 1994 simply because enough of us have received the polio vaccination. The virus has trouble finding bodies to grow in, and therefore it isn't in circulation. But when too few of us are vaccinated, we find ourselves in the midst of an outbreak, like the measles outbreak Minnesotans are living through right now.
But my children are vaccinated, so why should I worry about the measles outbreak or the unvaccinated lot who are allowing the measles virus to circulate throughout our community?
Vaccines are not a guarantee. They can't always provide complete immunity for every person every time. The MMR vaccine produces immunity in 95% of those who receive the first dose. Doctors intend for the second dose to catch those who did not build immunity after the first dose. Nonetheless, some who are vaccinated are still not immune.
Not everyone can be vaccinated. Some people are too immuno-compromised to receive the vaccine, others have allergies to some of the components, and some are too young to receive the vaccine. Many of those who died in this year's pertussis outbreak in California were too young to have completed the immunization against it.
And some people in our world have such weakened immune systems that their survival depends on the health of the community. The mother who has terminal cancer deserves to spend as many days as possible with her children without her life being cut short by a vaccine-preventable disease. Grandchildren do not want to lose their grandparents early due to a bout of influenza.
I care whether or not you vaccinate because I care not only about my children and their health, but I care about others in my community. I care about the people I see every day who have asthma or rheumatoid arthitis, and so I get my kids their shots, and I want you to do the same.