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What is the particular danger of giving a live attenuated viral vaccine?
AIt cannot raise protective immunity
BIt may mutate back to a harmful form
CIt always needs a booster each year
DIt kills every host cell that it enters
Answer & Solution
Correct answer: B. It may mutate back to a harmful form
1. Live vaccines are usually more effective than killed vaccines.
2. They carry a low but real danger that the virus reverts to its disease-causing form by back mutation.
3. A back mutation lets the vaccine virus readapt to the host and cause disease again, which can then spread.
4. Exactly that happened in Nigeria in 2007, where mutations in a polio vaccine led to an epidemic of polio.
5. Raising protective immunity is what a live vaccine does well, so the first option states the opposite.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 21 "Viruses", section 21.3 Prevention and Treatment of Viral Infections_
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