Also, I had heard said that the spike proteine was the "obvious best choice" based on the assumption that a race was going on to delivering the vaccine first. Because the spike proteine was a prior selected and already under study element. (Not because it was most favorable candidate for this exact societal situation.) And we have long known (many decades) that pharmaceuticals are notoriously problematic if not kept in check.
Discussion
Also, I wonder, if you consider it a "race" with proper (expert informed) qualification, whether Russia's solution would come out on top, for better choices and methodology and less risk and still timely. Because nobody seems to take an interest in the Sputnik V vaccine. (Well, outside of some scientific research evaluations.)