What kind of vaccine needs 7 doses at first place?

• Tetanus & diphtheria - 4 doses by 18 months, another at age 4-6, with doses every 10 years thereafter - most adults will get their 7th dose sometime after 25 when they get stitches
• Pertussis - similar 6 dose schedule by age 16, newer guidelines recommend a seventh dose in your 20s because the vaccine just isn't very good at conferring immunity
• Influenza - annual
• Oral ETEC (Enterotoxigenic E. Coli) - originally a cholera vaccine repurposed to be marketed to Western vacationers to the Caribbean. Wears off after a few months and needs a new booster dose with every new trip. Theoretical to reach 7 doses if you travel frequently and enjoy lighting money on fire because it's expensive and doesn't work.