The inactivated polio, hepatitis A, influenza (shot), and rabies vaccines are made this way. By killing the virus, it cannot possibly reproduce itself or cause disease. Using this strategy, viruses are completely inactivated (or killed) with a chemical. Watch this video to see how viruses are weakened to make vaccines. Find out more about what happens when the immune system doesn’t work properly. The limitation of this approach is that these vaccines usually cannot be given to people with weakened immune systems (like people with cancer or AIDS).
The advantage of live, "weakened" vaccines is that one or two doses provide immunity that is usually life-long. Find out more about these and other cells of the immune system. Because vaccine viruses don't reproduce very much, they don't cause disease, but vaccine viruses replicate well enough to induce "memory B cells" that protect against infection in the future. Whereas natural viruses reproduce thousands of times during an infection, vaccine viruses usually reproduce fewer than 20 times. Viruses usually cause disease by reproducing themselves many times in the body. The vaccines for measles, mumps, German measles (rubella), rotavirus, oral polio (not used in the U.S.), chickenpox (varicella), and influenza (intranasal version) vaccines are made this way. Using this strategy, viruses are weakened so they reproduce very poorly once inside the body. The strengths and limitations of each approach are described here. Several basic strategies are used to make vaccines, as shown in this infographic. To view the full-size infographic, click this photo or the link in the text.
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