Scientists are currently developing "self-spreading vaccines" aimed at infecting others from vaccinated to unvaccinated populations, according to National Geographic.

The "controversial" research by several groups of scientists are developing these "contagious" vaccines for Ebola, bovine tuberculosis, and Lassa fever in animals with the hopes these diseases will be less transmissible from animals to humans.

The vaccine would essentially be a genetically recombinant virus that infects anybody within a close enough proximity to the inoculated individual, so that one person could potentially spread the vaccine to many other unsuspecting people.

From National Geographic:

Imagine a cure that's as contagious as the disease it fights—a vaccine that could replicate in a host's body and spread to others nearby, quickly and easily protecting a whole population from microbial attacks. That's the goal of several teams around the world who are reviving controversial research to develop self-spreading vaccines.

Researchers are currently developing self-spreading vaccines for Ebola, bovine tuberculosis, and Lassa fever, a viral disease spread by rats that causes upward of 300,000 infections annually in parts of West Africa. The approach could be expanded to target other zoonotic diseases, including rabies, West Nile virus, Lyme disease, and the plague.