I think what Professor Jonathan Edwards means by evidence is evidence of the highest standard, which I think would be phase III clinical trials. That I believe is the sort of evidence required before the UK NHS will consider allowing the routine prescription a drug or therapy.
However, there are also lower standards of evidence, such as the single
study by Dr Lerner on Valtrex and/or Valcyte for Herpesviridae-associated ME/CFS, which followed 142 ME/CFS patients, for up to six years in some cases.
This evidence would not be accepted by the NHS, but as a patient you may feel that there is enough evidence there for you to give it a try.
If you look at Table 3 (copied below) from the Lerner study, you see how the average
Energy Index Point Score (EIPS) of the antiviral-treated patients improved slowly over the years. The table shows the figures at three month intervals, so the row that I have highlighted in green shows the improvement in the EIPS (mean) after two years.
Table 3. Improvements in Energy Index Point Score over
time for ME/CFS patients given Valtrex and/or Valcyte
You can see that on average, Dr Lerner's patients started with an EIPS (mean) of just over 4, and two years later, on average they achieved a score of just over 6. So that is a two point increase over 2 years.
Note that on the EIPS:
Level 4 = Out of bed sitting, standing, walking 4 - 6 hours per day (the rest of the day in bed).
Level 6 = Daily naps in bed, may maintain a 40 hour sedentary work week plus light, limited housekeeping and/or social activities.
Dr Lerner found that 75% of the patients he treated increased their Energy Index Point Score by at least 1 point. So most patients do have some response.
When the patient only had EBV infections, they were treated with Valtrex (or Famvir) 1,000 mg every six hours.
If the patient had HHV-6 or cytomegalovirus, they were give Valcyte 450 mg x 3 daily.
What not very clear in Dr Lerner's study is the relative efficacy of antiviral treatment for EBV-associated ME/CFS using Valtrex (or Famvir), compared to the efficacy of antiviral treatment for HHV-6- or cytomegalovirus-associated ME/CFS using Valcyte. This is because Lerner combines all his patients who have one or more of these 3 Herpesviridae infections into a single group, so in his data you cannot focus solely on for example the efficacy of Valtrex for EBV-associated ME/CFS.
Note: the fact that this study showed ME/CFS patients improving on antivirals does not prove that ME/CFS is necessarily a viral disease. The viruses involved may simply be exacerbating the pathophysiology of ME/CFS, which may well be an autoimmune pathophysiology.