So the fact that I never had the flu vaccine likely made me less susceptible to the Covid-19 bug, a coronavirus.
Yes, the natural human antibody response to invaders is a broader spectrum response than the very specific agents resulting from a vaccine. The human response has to be broader because it is searching for what will work and throwing more than one specific counter attack at the invader. Then the T cells remember what was produced and what worked, bringing out the same army next time.
Yes!