This is the 8440th most frequent Chinese word.
pfize
The word "pfize" does not exist in Chinese. It may be a misspelling or misunderstanding.
Pfizer is used here to refer to the organization where the mentioned person works.
我妹妹在辉瑞公司工作，她从事研发工作。
My sister works at Pfizer Inc., and she is engaged in research and development.
Pfizer is referred to as the name of a company in this sentence.
辉瑞公司是研发新冠疫苗的制药企业之一。
Pfizer is one of the pharmaceutical companies that developed the COVID-19 vaccine.
Here, Pfizer refers to the vaccine that the company produces.