How Vaccinations Work

Many people know that vaccinations are given to people and animals to help protect them from certain diseases, but most people don’t really understand how vaccines actually work. Understanding how vaccines do what they do can raise your appreciation for how important they are, for you, your children and your pets.

The Science Behind Vaccination

When a person or animal gets a disease, their immune system produces antibodies to fight that disease. This can take some time. In the meantime, sickness occurs that only goes away when the antibodies begin fighting the disease.

However, if a person or animal gets the same disease again, the antibodies will begin to fight the disease faster. The immune system has a kind of memory and will not have to start from scratch when producing antibodies a second time.

This is where vaccinations come in. Vaccinations introduce a dead or weakened form or a disease into the body. The immune system gets a chance to recognize the disease and create antibodies for the weakened disease. Because the disease is not at its strongest, usually people do not get sick from it. However, if they contract the disease in a stronger form later, the immune system will already recognize it and be able to produce antibodies to fight it off.

Types of Vaccines

Vaccinations that are given to fight off disease can be in one of four forms:
  • Altered live bacteria or viruses that can no longer cause disease: Bacteria and viruses are inactivated using chemicals such as formaldehyde.

  • Dead bacteria or viruses: Dead cells can no longer infect a person but will still create an immune response.

  • Parts or portions of bacteria or viruses: Antibodies can form against part of the bacteria or virus. Some of the newest vaccines are made this way, including hepatitis A and hepatitis B.

  • Toxoids, which are toxins from bacteria that have been altered to be harmless: Toxoids are treated with heat or chemicals, such as formalin to make them inactive. Tetanus and diphtheria vaccines fall under this category.

Another type of vaccine, called a live attenuated vaccine, is made up of a naturally occurring germ. This type of vaccine can cause a slight infection, but will not cause a serious occurrence of the disease. Live attenuated vaccines include:

  • measles vaccine
  • mumps vaccine
  • oral polio vaccine
  • rubella vaccine
  • varicella vaccine (also known as chicken pox vaccine).

Re-Vaccination and "Boosters"

In some cases, vaccines may not last forever and may need to be re-administered after a certain period of time. This is sometimes referred to as a "booster" shot or a re-vaccination.

Children are vaccinated for certain diseases at infancy, before beginning elementary school and before entering college. Adults need re-vaccination on very seldom occasions, but may require vaccines before entering a foreign country or taking on certain types of work.

Animals need to be re-vaccinated for most diseases every one to three years. A veterinarian can recommend specific vaccinations and a vaccination schedule.

Resources

Maybury Okonek, Bonnie A., and Peters, Pamela A. (n.d.). Vaccines—How and Why? Retrieved October 26, 2007, from the Access Excellence Web site: http://www.accessexcellence.org/AE/AEC/CC/vaccines_how_
why.html.
 
National Network for Immunization Information (2007). Why Immunize? How Vaccines Work. Retrieved October 26, 2007, from the NNII Web site: http://www.immunizationinfo.org/parents/howVaccines_
work.cfm.