Notes
Live vaccines contain living pathogens. These pathogens invade cells within the
body and use those cells to produce many copies of themselves, just as their
more harmful counterparts would. The "similar pathogen" and "attenuated"
vaccines discussed in this feature are examples of live vaccines. Although
these vaccines trigger a full immune response, there is a small risk of the
viruses within evolving into more-virulent strains. Non-live vaccines contain
agents that do not reproduce in the body. "Killed," "subunit," and "toxoid" are
examples of non-live vaccines. These vaccines trigger a partial immune
response. Genetic vaccines are non-live vaccines that trigger a full immune
response.
The procedures outlined in this feature have been greatly simplified. Also,
some steps are meant to show what is done but not how. For example, a gene
cannot be plucked out of DNA using tweezers, and there's no box-like device
called a purifier that can extract toxins from bacteria as well as viruses from
pus.
