Open Philanthropy's recent blog post announcing new hires in South Asian Air Quality and Global Aid Advocacy states that the U.S. President's Emergency Plan for AIDS Relief (PEPFAR) "has plausibly saved tens of millions of life-years since it was created in 2003." The post provides a link to a PEPFAR page that credits the program with "saving over 20 million lives", but unfortunately that page doesn't give a source for the estimate. The same estimate is mentioned in the PEPFAR Wikipedia page, but the other listed sources either merely repeat that figure or do not even give an estimate (Fauci & Ensinger 2018 is entitled 'PEPFAR — 15 Years and Counting the Lives Saved' but the paper does not actually count the lives saved by the program; it rather lists various intermediate outputs such as the number of people given retroviral therapy or the number of voluntary male circumcisions supported).
So, does anyone happen to know the source of the 20 million lives estimate, or is aware of other attempts to estimate the program's impact, measured in lives or life-years saved? Background: I'm interested in this mostly because I would like to expand the list of examples of successful aid programs in the Wiki entry on foreign aid skepticism.
(This question was adapted from a draft email I wrote to the Open Phil post author. After finishing the draft, I realized I didn't have his email address and couldn't find it online.)