Vaccine Science

How vaccines work
How vaccines are made

How vaccines work
A person who has been ill with a disease is less likely to get the disease again than someone who never had it. This is because when a person is sick, their body makes infection-fighting antibodies. After the person recovers, these antibodies move around in the person’s body and watch for that disease again. If the antibodies detect disease, they quickly signal the body to start making more antibodies to fight the infection. This person is considered to be immune from the disease and may not even know that he or she was exposed to it again.

A vaccine works like the first encounter with disease in that it allows the body to make antibodies that will circulate and watch for the disease to come again. The difference between a vaccine and the first encounter with a disease is that the vaccine causes immunity without causing disease.

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View a video clip about how someone becomes immune to a disease, by selecting "What is immunity?" in the "Vaccines and Your Baby" video»

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How vaccines are made
It takes several years to make a vaccine and test it for its safety and utility. There are currently a handful of different approaches used to make vaccines:

• Use a single piece of the virus (purified protein vaccine)– e.g., hepatitis B vaccine
• Link a part of the bacteria to a helper protein (conjugate vaccine) – e.g., pneumococcus, Hib, and meningococcus
• Purify a toxin produced by the bacteria (toxoid vaccine) – e.g., diphtheria, tetanus, and pertussis
• Inactivate the whole virus (inactivated vaccine) – e.g., polio, hepatitis A, and influenza
• Use a live form of the virus that has been weakened (live, attenuated vaccine) – e.g., measles, mumps, rubella, and varicella (chickenpox).

To learn more about how some of these vaccines are made, view the "Vaccines and Your Baby" video, and go to the "Click here to learn about specific vaccines" section.

Learn more about how vaccines are made» 

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