Search of COVID-19 vaccines.

Keywords used to pre-select vaccine listings from the original dataset. Words are truncated to include different suffixes (e.g., vaccin yields vaccine, vaccination, vaccinate, etc.)用于从原始数据集中预筛选疫苗相关条目的关键词。所有单词均经过词干截断处理，以覆盖各类后缀变体（例如，以vaccin为词干可涵盖vaccine、vaccination、vaccinate等词汇）。