We Now Have The Technology To Develop Vaccines That SPREAD THEMSELVES

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https://www.newscientist.com/article/mg24732960-100-we-now-have-the-technology-to-develop-vaccines-that-spread-themselves/

A more radical approach relies on inserting a small piece of the genome of the infectious disease agent into a benign virus that spreads naturally through the animal population. As this transmissible vaccine spreads from animal to animal, it immunises them against the target infectious disease, vastly increasing immunity within the animal population and reducing the risk of spillover to humans.