Why do some vaccines use weakened or inactivated germs?
Quick Answer
These vaccines expose the immune system to the pathogen in a form that cannot usually cause full disease but still teaches recognition. They have been used for many decades, including in polio and yellow fever vaccines.
The Full Story
Live-attenuated vaccines use a weakened version of the pathogen, while inactivated vaccines use germs that have been killed or otherwise rendered non-replicating. Both strategies let the immune system see the germ’s antigens and build protection. Live-attenuated vaccines often create strong, long-lasting immunity, while inactivated vaccines are safer for some people and cannot replicate. Classic examples include the oral polio vaccine for live attenuation and the inactivated polio vaccine for killed virus. The choice depends on the disease, the vaccine platform, and safety considerations.
Key Facts
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"Why use a weakened germ as a vaccine? It’s a controlled lesson for the immune system."
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