Body takes repeat threat way more seriously. That's the reason second dose of vaccine mRNA creates about 10x more antibodies. Almost all kids vaccine require a second or even 3 shots with months of gap in between to create stronger immunity. (https://www.cdc.gov/vaccines/schedules/hcp/imz/child-adolesc...)

If you keep a tab on the news you might have seen antibody level from covid vaccines drops significantly over time. Actually same is true for people already have covid; natural protection wanes off within few months.