booster

https://doi.org/10.1351/goldbook.12961
Portion of an immunizing agent given at a later time to stimulate the effects of a previous dose of the same agent.
Source:
PAC, 2012, 84, 1113. (IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)) on page 1136 [Terms] [Paper]