When someone who has had a mild case of COVID is vaccinated, the antibody level in their blood doubles compared to an unvaccinated person who has been infected by the virus. Their antibodies are also better able to prevent spike-ACE-2 interaction.Université de Montréal. “COVID-19: The older you are, the more antibodies you have, study finds.” ScienceDaily. http://www.sciencedaily.com/releases/2021/11/211108081455.htm (accessed November 9, 2021).
A very small study with very interesting findings.
Also see Thinking About a Booster Shot?