the 'B' and 'T' cells they create are so important.
While the SARS-CoV-2 'Spike' continues to mutate, thus making infection more likely (i.e. vaccine designed neutralization (for "Wild Type" diminished)...a vaccinated person has the advantage of being prepared to fight it due to the virus killing combination of those B and T cells resident in lymph nodes and bone marrow. That's why you see proportionally so few hospitalizations and deaths from COVID-19 as compared with unvaccinated persons.
Link: https://youtu.be/iTMapltm6bA