You'd have to ask the Pfizer / BioNTech press staff, since they were the source.
Later down in this article, they clarify with some hard numbers: "Researchers observed 18 Covid-19 cases among the 1,129 participants who were given a placebo, and none among the 1,131 volunteers who got the vaccine. The data has yet to be peer reviewed."
So Pfizer/BioNTech is reporting 100% efficacy on a non-peer-reviewed study where 1.5% of the control group contracted the disease (news article doesn't say how "contraction of disease" was identified, whether that was antibody presence or symptoms).
News has a bad habit of reducing complex circumstances to headlines that appear yes-or-no.
Later down in this article, they clarify with some hard numbers: "Researchers observed 18 Covid-19 cases among the 1,129 participants who were given a placebo, and none among the 1,131 volunteers who got the vaccine. The data has yet to be peer reviewed."
So Pfizer/BioNTech is reporting 100% efficacy on a non-peer-reviewed study where 1.5% of the control group contracted the disease (news article doesn't say how "contraction of disease" was identified, whether that was antibody presence or symptoms).
News has a bad habit of reducing complex circumstances to headlines that appear yes-or-no.