I like to recommend this webcast by Professor Anna Lok, presented by invitation at the recent CROI:
webcast: https://www.croiwebcasts.org/console/player/51538?mediaType=slideVideo&
This is my interpretation, and it is not necessary that of Prof. Anna Lok. The new partial cure is when your serum hbvdna is zero or undetectable, but HBsAg is still positive. Because serum hbvdna is zero, that means there is no cccDNA (zero or inactive) in the liver. Therefore, there is no template to produce new Hepatitis B virions. The still detectable serum HBsAg comes from the hbvdna integrated into the human genome in the cells of the liver. The integrated hbvdna cannot create a new HBV. It became part of the human genome and cannot be lost during mitosis of the liver cells. It can only be eradicated when its liver cell dies. No new drugs are needed to achieve this functional cure because cccDNA can be lost from liver cells during mitosis during natural liver cell turnover. The only thing needed is time, no new external infection and no internal cycling of hbvdna. Existing TDF, TAF, and Entecavir can prevent the production of new viral capsids with hbvdna. Therefore over time, there will be no cccDNA in the liver.
Also, inactive HBV patients can achieve this new functional cure without taking any HBV drugs.