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Ultrasound can push vaccines into the body without needles
(www.newscientist.com)
This is a most excellent place for technology news and articles.
First of all, thank you for taking the time help me understand. I didn't know about past vaccines that used the system.
They didn't use this system. There are other needleless systems, primarily jet systems that use high pressure.
The smallpox vaccine was put on a sugar lump that children then ate (It really was a different time) And even after going through the digestive tract it still worked.