In this case the appropriate definition of "prevention" and "what is prevented" is to be found in the protocol of the trial [1], not in a dictionary of the Eng

In this case the appropriate definition of "prevention" and "what is prevented" is to be found in the protocol of the trial [1], not in a dictionary of the English language. If I am reading correctly (but do correct me if I am wrong because I am not 100% certain), only symptomatic cases are counted. Hence, it is quite possible for the vaccine to stop the symptoms, but not the transmission between individuals. [1] https://www.nejm.org/doi/suppl/10.1056/NEJMoa2034577/suppl_file/nejmoa2034577_protocol.pdf https://www.nejm.org/doi/suppl/10.1056/NEJMoa2034577/suppl_f...