The smallpox vaccine is a treatment for monkeypox as well is made using the causative agent of cowpox, that is, poxvirus. All these three viruses belong to the same family, poxvirus, and are thus very similar to each other due to which a single vaccine can provide protection against these viruses. For more information- https://redcliffelabs.com/myhealth/lifestyle/overall-health/monkeypox-symptoms-and-treatment/