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Children's Health

Vaccine efficacy



Does the minimal bleeding that is observed right after an IM injection of a vaccine affect its efficacy?


Thank you for your question about vaccines and how effective they are.  Vaccines are injected either below the skin or in the muscles.  Either way they are injected can cause bleeding from the skin and would not cause issues with how effective the vaccine would be.  Please be assured that the vaccine is still effective if there is bleeding or even a small amount fluid at the site.

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Response by:

Allison A Macerollo, MD Allison A Macerollo, MD
Clinical Assistant Professor of Family Medicine
College of Medicine
The Ohio State University