Single antibody, yes. A lot of different antibodies are made. The ones that seem to act "better" get made the most. As far as can be understood, the immune sys

Single antibody, yes. A lot of different antibodies are made. The ones that seem to act "better" get made the most. As far as can be understood, the immune system does random self-mutation of its antibody generation and starts picking winners at local maxima. The result is antibodies start targeting various parts of viruses, bacteria, and other invaders. Binding and neutralizing the spike protein neutralizes the virus, so the vaccines used it. Upside: immediately effective vaccine. Downside: Its possible random antibodies in natural infection could target another critical protein to covid19 that is not on the spike, but also shuts down replication. So that's also in the field of study for covid, as well as influenza, vaccines. Is there some part of the viruses we could target instead of the spike(or the influenza hemagglutinin) that would cause immunity against the entire class of virus? Such is the search for a universal influenza vaccine.