Thank you for your question. This is not necessarily the case. A vaccine is a biological substance that is formulated from components of or a weakened form of an infectious disease. When a vaccine is injected into to the body, it elicits an immune response in which protective antibodies are developed against that specific infectious disease. If this does not work, it is possible that the initial vaccine did not elicit this immune response due to the quality of the vaccine or you may require a booster to elicit this immune response. The varicella zoster vaccine for example, can lose its protective strength after several years and may require a booster vaccine to redevelop immunity.
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