Why are vaccines important for my child?

Vaccines help prevent contagious diseases that are either viral or bacterial. The prevention of viral diseases is extremely important, since they do not respond to antibiotics. With the increase of bacterial resistant diseases, prevention of bacterial forms is also important. Vaccine preventable diseases are not a thing of the past. With fewer people immunized, many developed countries, including the United States, are seeing a resurgence of these diseases.

Click here to view the Centers for Disease Control explanation of what diseases are vaccine preventable and a description of their potential harmful effects.

What is herd or community immunity?

Community immunity refers to the concept that if a critical portion of the community is immunized, infectious diseases have a hard time transmitting from person to person and causing an outbreak. The pictures below illustrate the basic concept of community immunity.

Illustration of Community Immunity (also known as “herd” immunity)

 

 

Community immunity is extremely important for those persons who cannot be vaccinated due to health risks, for instance children who are too young or with severely compromised immune systems (like Leukemia).

Vaccine preventable diseases are not a thing of the past, England and the rest of the United Kingdom have been experiencing a Measles outbreak since April 2013 due to their extremely low Measles and Rubella rates over the past ten years, other European countries experiencing outbreaks since the beginning of 2013 include  Switzerland, Ukraine, France, Spain, Italy, and Germany. In the United States, some areas (including southern Wisconsin) are no longer covered by community immunity because rates are so low.

What is a "critical portion" of the community?

Community Immunity Thresholds Estimates
For Selected Vaccine-Preventable Diseases

Vaccine-Preventable Disease

Level of Community Immunity

Diphtheria

85%

Measles

94% or more

Whooping Cough

94%

Rubella

85%

Smallpox

85%

The values in this table are estimates and can vary according to the method used to calculate them. The number of factors involved in community immunity makes the calculation of exact thresholds very complex.

The protection offered by community immunity is evident from results of many vaccination programs and from theoretical estimations. These estimations tell us that for an infection to persist (spread) in a community, each infected individual must be able to transmit the infectious agent to other individuals. Otherwise, the disease will disappear.

Several factors involved in the transmission of infectious diseases concern the measurement of community immunity:

  • The biologic properties of the viruses or bacteria: Some diseases are more easily transmitted than others, thus affecting community immunity thresholds. The greater the transmissibility, the higher the threshold needs to be to prevent spread of the disease.
  • The rate of contact among susceptibles and immunes in a population: Susceptibles are protected by community immunity only when they interact with immunes rather than with other susceptibles.
  • The number of susceptibles in the population: Immunes have to so far exceed the number of susceptibles in any community that contacts between susceptibles are rare events.

All these factors can be used to predict the impact of an immunization program in a population and to set up immunization coverage goals. Thus community immunity plays an important role in public health.

(Orginal data can be found here on the National Network for Immunization Information)

 

Rates in southern Wisconsin have been averaging close to 65 - 70% in children 18-36 months for since 2008. Dane County is slightly higher at 70 - 80%.

These rates are much too low to depend on community immunity for your child. Rates among adults are even lower with the most recent CDC estimates at below 6%. Babies especially depend on community immunity. Four out of five children under the age of six months who fell ill with whooping cough (Pertussis) caught it from a household member. If you have a young child, it is recommended that you also update your vaccines.

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