In an unexpected announcement, the Centers for Disease Control and Prevention on Wednesday sent a message to state leaders: be ready to distribute a COVID-19 vaccine by November 1st.

The news came in a memo from CDC director Robert Redfield to state governors. In it, he says the McKesson Corporation will help in distributing the vaccine to local and state health departments and medical facilities.

Just two days ago, a different U.S. vaccine entered Phase 3 trials with 30,000 test subjects.

Although Redfield has offered no details about the vaccine that’s coming in November, it’s unlikely it completed all phases of testing. According to the FDA, Phase 3 alone usually takes one to three years.