Killed Virus vs. Modified Live Vaccines

Vaccines for different diseases can be made of either dead cells of a virus or modified cells of the live virus. Both types of vaccines will stimulate an immune response from the body.
 
When a person is exposed to a disease, the immune system must learn to produce antibodies, or disease fighters, that will kill the disease. This can take some time, however, and in the meantime, the person is sick. The next time the person is exposed to that disease, the immune system will already know how to fight it off and the person will most likely not develop symptoms.
 
Vaccines work to prevent the person from having to get sick the first time. They introduce dead or weakened cells of a disease into the body, which will also create a response from the immune system. The immune system will still produce antibodies against the disease and will know how to fight it off if a person is exposed to it in the future. However, vaccines may need to be given in a series or as follow-up vaccines, called boosters, to be fully effective.

Killed Virus Vaccines

As the name suggests, killed virus vaccines are vaccines that are made from dead disease cells. Killed virus vaccines are also sometimes known as inactivated virus vaccines. Viruses are inactivated through the use of chemicals, such as formaldehyde. A few examples of a killed virus vaccine are:
  • influenza vaccine
  • polio vaccine.
Killed virus vaccines cannot cause any infection in people as some other vaccine types can.

Modified Live Vaccines

Modified live vaccines, also known as live attenuated vaccines, are made from the virus cells themselves. The cells are passed through multiple cell cultures so that their ability to cause disease is severely decreased.

However, some people who get modified live vaccines may develop slight symptoms or infection. This will not be as severe as getting a full-blown version of the disease and will not be severely harmful.

Some examples of modified live vaccines include:

  • chicken pox vaccine (also known as varicella vaccine)
  • measles vaccine
  • mumps vaccine
  • oral polio vaccine
  • rubella vaccine.
While killed virus vaccines and modified live vaccines are the most common vaccine types, there are also two other types of vaccines.

Other Vaccine Types

Two other commonly found vaccine types are:
  • component vaccines
  • toxoid vaccines.

Component vaccines are a newer type of vaccine and use only a portion or a part of the disease cells to protect against infection from the whole germ. This type of vaccine cannot cause disease or infection.

Component vaccines include:

  • haemophilus influenzae type b (Hib) vaccine
  • hepatitis A vaccine
  • hepatitis B vaccine
  • pneumoccocal conjugate vaccine.

Toxoid vaccines are made by using heat or chemicals to destroy the toxicity of the disease cells. Toxoid vaccines also do not cause symptoms or infection to appear in people.

Toxoid vaccines include:

  • diphtheria
  • tetanus.

All of these vaccine types are effective at preventing future disease in both people and animals.

Resources

Cates, Lynn (2000). The Main Types of Vaccines. Retrieved November 7, 2007, from the Dr. Spock Web site: http://www.drspock.com/article/0,1510,4866,00.html.

National Network for Immunization Information (2007). How Vaccines Work. Retrieved November 7, 2007, from the NNII Web site: http://www.immunizationinfo.org/parents/
howVaccines_work.cfm.