why is more tough to make a viral vaccine as compared to bacteria vaccine?
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Answers
Answer:
Using this strategy, viruses are weakened so they reproduce very poorly once inside 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. Viruses usually cause disease by reproducing themselves many times in the body. Whereas natural viruses reproduce thousands of times during an infection, vaccine viruses usually reproduce fewer than 20 times. 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. Find out more about these and other cells of the immune system.
The advantage of live, "weakened" vaccines is that one or two doses provide immunity that is usually life-long. 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). Find out more about what happens when the immune system doesn’t work properly.
Explanation:
Answer:
Because viral DNA sequences changes each time , so it is difficult