A friend of mine sent me a series of complicated tracking charts for COVID-19 in the United State. Because it's an RNA virus, it frequently mutates, so different strains are produced as it moves along. That's how they get this data. It's not clear yet how this might affect developing a vaccine. Typically, the vaccine is not against the RNA virus itself, but rather against the "signal protein" on the surface of the virus. So long as that does not substantially change with the mutations, a reliable vaccine might be possible. However, on another note, some old testing in animals using prior coronaviruses yielded very mixed results. The worst, in my opinion, was a vaccine that seemed to work, but when the animals were then exposed to the actual virus, they had a HYPER-immune response which created a kind of autoimmune condition in the body, harming body organs. This is why it takes a while to develop worthy vaccine and serum antibody treatments.
Anyway, here is the conclusion data about COVID-19 spread in the United States (and some elsewhere).