I believe she is speaking to the vaccine effectiveness waning over time against severe disease. The first frames of the video also support what I am saying plus it is the theme of her entire presentation supporting their decision to require the booster shot for their green card vaccine passport. What's interesting is in part of her argument she states that the implementation of the green card didn't actually reduce the number of cases meaning the segregation of society didn't have an effect which is the really stunning admission IMO