Vaccinations Modified Live Killed Vaccines

Vaccines for different diseases can be made of either dead cells of a virus or modified cells of the live virus, both of which 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 be a lengthy process, however, leaving the person sick in the meantime. The next time the person is exposed to that disease, the immune system will already know how to fight it off and the person usually won’t develop symptoms.

Vaccines contain dead or weakened cells of a disease, which will also create a response from the immune system. The immune system will produce antibodies against the disease and will know how to fight it off if a person is exposed to it in the future. Certain vaccines may require a series of vaccines, including boosters — or re-vaccinations — for maximum effectiveness.

Killed Virus Vaccines

As the name suggests, killed virus vaccines consist of dead disease cells. Also known as inactivated virus vaccines, these viruses are inactivated through the use of chemicals, such as formaldehyde. A few examples of killed virus vaccines are the influenza and polio vaccines. Killed virus vaccines can’t cause infection in people, unlike other vaccine types.

Modified Live Vaccines

Modified live vaccines — also known as live attenuated vaccines — contain the virus cells themselves. These cells pass through multiple cell cultures, decreasing their ability to cause disease. Although some people may still develop slight symptoms or infection, it won’t be as severe as a full-blown version of the disease. Some examples of modified live vaccines include the:

  • Chicken pox vaccine (the varicella vaccine)
  • Measles vaccine
  • Mumps vaccine
  • Oral polio vaccine
  • Rubella vaccine.

Other Types of Vaccines

While killed virus vaccines and modified live vaccines are the most common vaccine types, there are two other types of vaccines, including component vaccines and toxoid vaccines.

Component vaccines — a newer type of vaccine — uses only a portion or a part of the disease cells to protect against infection from the whole germ. This type of vaccine can’t 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. Like component vaccines, toxoid vaccines — including the diphtheria and tetanus vaccines — won’t cause symptoms or infection.


Cates, L. (2000). The Main Types of Vaccines. Retrieved November 7, 2007, from,1510,4866,00.html.

National Network for Immunization Information. (2007). How vaccines work. Retrieved November 7, 2007, from