The finished policy memo should identify a public health issue, describe the background and policy landscape around the issue, and propose policy alternatives to address the issue based on policy innovations from other locations. The final policy memo document will be 4-5 pages (single-spaced, excluding references).
You can look at sites like APHA or CDC for ideas on policy topics:
https://www.apha.org/topics-and-issues
https://www.cdc.gov/phlp/news/current.html
I attached the topic I came up with that you can expand on.