Question

vaccines are introduced ___&___​

Answer 1

Answer:

Explanation:

A vaccine works by training the immune system to recognize and combat pathogens, either viruses or bacteria. To do this, certain molecules from the pathogen must be introduced into the body to trigger an immune response. These molecules are called antigens, and they are present on all viruses and bacteria

They were introduced by Edward Jenner who  developed the first vaccine in 1796 using cowpox to inoculate against smallpox.

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Answer 2

Explanation:

#Vaccine were introduced by Edward Jenner.

#It was against small pox.