A booster shot is a single dose of a vaccine that is given after the initial vaccination series to help maintain immunity. However, there are many synonyms that can be used to refer to a booster shot. Some of the common synonyms include reinforcement shot, follow-up dose, secondary vaccine dose, and supplementary immunization. Additionally, other synonyms include interim shot, refresher dose, strengthening shot, and maintenance immunization. These terms all refer to the same concept of receiving an additional dose of vaccine to help maintain immunity against a particular disease. Ultimately, using different synonyms can help add variety and clarity to discussions about vaccinations and booster shots.