The full press release nowhere says that those vaccinated were exposed to the virus. In fact an argument rages elsewhere about the ethics of doing any such thing although we can guess that authoritarian regimes have carried out such testing. The salient paragraph in the press release says “ Upon the conclusion of those discussions, the evaluable case count reached 94 and the DMC performed its first analysis on all cases. The case split between vaccinated individuals and those who received the placebo indicates a vaccine efficacy rate above 90%, at 7 days after the second dose. This means that protection is achieved 28 days after the initiation of the vaccination, which consists of a 2-dose schedule. As the study continues, the final vaccine efficacy percentage may vary.”

The full press release can be found here - https://www.pfizer.com/news/press-re...didate-against