This is the 8113th most frequent German word.
impfstoff
Vaccine.
In this sentence, 'Impfstoff' refers directly to the medical substance used for immunization.
Der Impfstoff gegen Grippe ist dieses Jahr sehr effektiv.
The vaccine against flu is very effective this year.
Here, 'Impfstoff' is used to denote a specific vaccine currently in development or distribution.
Viele Menschen warten auf den neuen Corona-Impfstoff.
Many people are waiting for the new COVID vaccine.
In this instance, 'Impfstoff' highlights the process and field of creating vaccines rather than a particular vaccine itself.