What are the types and mechanisms of traditional vaccines?

There are several different types of traditional vaccines, each of which has a different mechanism. 

Live-attenuated or live vaccines

Live vaccines use a weakened (or attenuated) form of the germ that causes a disease. These vaccines are highly effective because of their similarity to the natural infection that they prevent. One to two doses can provide lifetime protection against a germ and the disease it causes.  However, because they contain a small amount of the live virus, they pose a higher risk particularly to someone with a weakened immune system. Live vaccines are used to protect against measles, chickenpox, rubella, and mumps.

Inactivated vaccines

Inactivated vaccines are safer because they don’t contain any part of the live virus. However, they don’t provide as strong immunity as live vaccines and give short-lived immune protection. Several doses, known as booster shots, may be required over a period of time for ongoing immunity. Inactivated vaccines are used to protect against flu, Hepatitis A and rabies.

Toxoid vaccines

Toxoid vaccines are made using a small portion of the toxin produced by the germ that causes diseases. Booster shots are often required for continued protection against that disease. Like some other types of vaccines, you may need booster shots to get ongoing protection against diseases. Toxoid vaccines are used to protect against tetanus, and diphtheria.

Viral vector vaccines

In viral vector vaccines, a modified version of a different virus is used as a vector to provide protection. Scientists use different viruses as vectors including measles virus, influenza, adenovirus, and vesicular stomatitis virus (VSV). Viral vector vaccines are used to protect against COVID-19

Subunit, recombinant, conjugate, and polysaccharide vaccines

Subunit, recombinant, conjugate and polysaccharide vaccines use specific parts of a germ or a virus, like a protein or a sugar, in order to trigger an immune response. Using a specific part of the germ gives these vaccines the ability to trigger a very strong immune response. However, they still need booster shots at regular intervals over time. These vaccines are suitable for individuals with long-term health conditions and weakened immune systems. These vaccines are used to create protection against whooping cough, Hepatitis B, shingles, human papillomavirus (HPV), and meningococcal disease.