I think research is ongoing about the Delta variant (as it would with a relatively new strain), which is another mutation/strain that developed rather well in India, as it was easy to latch onto hosts there, in those conditions, especially at political rallies. But like other strains, one can also build antibodies that will combat that strain, and if there are vaccines that aren't yet effective, there will be new vaccines for that delta variant. A list of all the strains is here: https://nextstrain.org/ncov/

Immunotherapy is another term used to redefine the vaccine as a therapy, instead of a method of building antibodies. These antibodies will - if there are enough - kill the virus, rather than offer therapy.

If fewer people are suffering from the virus, it will have fewer opportunities to spread to new hosts and mutate. Helping the body build antibodies is part of this process with the vaccine. One can track the spread in different countries, here: https://www.worldometers.info/coronavirus where there are graphs that show a general trend downward in infections, depending on which graph you consult.

Regarding the Canadian poster, those diseases are rather old, and thus the percentage of 'success' is higher, now, decades later. The "cases then" section addresses annual cases in Canada many years ago. COVID19 annual cases in Canada would be half of 1,670,240 (in each or 2 years), and thus this number would be much higher on that chart. Of the 240 [EDIT: million] COVID cases globally, 217 [EDIT: million] have recovered. I could be wrong, but that's a 90% recovery rate, if we can trust those numbers. India, Brazil and China have underrepported their numbers. At this rate - within a year or two - the percentage of recoveries should be closer to 99%.