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Hopefully broad based enough to neutralize the coronavirus pandemic. The main problem is the tendency of the coronavirus, especially CoViD-19, to mutate. It is documented to mutate relatively frequently. For example, the European version of CoViD-19 is a bit different from the American version. The importance of this will become clearer as treatments emerge.
As I said early on, an effective vaccine is going to prove challenging. More expert opinions have been published echoing that difficulty.