VACCINES

Different Types
of Vaccines
Imagine that a new infectious disease emerges somewhere
in the world and begins to spread around the globe. The
infectious agent jumps easily from person to person
through the air, and it attacks the lungs, causing terrible
coughing, fever, pneumonia, and sometimes paralysis of
the respiratory system. Scientists quickly determine that
disease X is caused by a new species of toxic bacterium.
They call it “bacterium X.” Unfortunately, bacterium X
is difficult to fight because it resists most antibiotics, the
kind of drug used to treat bacterial infections.
Everyone agrees a vaccine against bacterium X is needed,
but how would scientists go about creating one? First,
researchers would carefully study bacterium X. They
would figure out what nutrients it requires. They would
examine how it damages lung tissue. Geneticists would
analyze bacterium X’s genes. Immunologists would
explore how the immune system responds to bacterium
X and why the body sometimes fails to fight off this
microbe. They would identify antigens from X that best
stimulate the immune system. Other scientists would
discover and study the toxin secreted by bacterium X.
Once scientists had some basic information about
bacterium X, they could begin designing vaccines that
might work against it. Following are some of the options
that researchers might pursue. They will give you an
idea of the main types of vaccine strategies. (This imaginary
new disease is caused by a bacterium, but scientists
would use approaches similar to those outlined below
to develop a vaccine against a new virus.)
UNDERSTANDING VACCINES 21