What is the difference between a booster shot and a regular COVID-19 shot?

What is the difference between a booster shot and a regular COVID-19 shot?

Booster shots are given to people who are likely to have developed a strong immune response with prior vaccination, in order to help increase, or boost, the immunity they already have. This is because there is some evidence from clinical trials that antibodies produced after the first two shots decline over time. Jan 26, 2022

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