I had treatment for Lyme disease in spring 2022, Doxyhexal - described as "a broad-spectrum tetracycline-class antibiotic". It was fairly effective, the symptoms faded and a blood test several weeks later showed that the offending bacteria were in retreat. Since a friend of mine had needed four courses of antibiotics before his Lyme was actually fixed, I asked them to check those values the next time I needed a blood test (maybe a year later). I'm back, baby.
The 2023 treatment was some other antibiotic being pumped directly into my bloodstream at the doctor's surgery for (I think) 6 days in a row - I think there was a weekend in there. Waiting a few weeks, a subsequent test showed the values had dropped again.
Fast forward to early 2025, I had another routine blood test (normal at my age) and I asked them to check those values again. Things are ok now.
I don't know why the Doxyhexal ultimately failed, but it did.