Jo*mar, the doses varied a lot (between 1 and 10 g/day when Vitamin C was taken by mouth and between 500 mg i.v. daily to 100 g i.v. three times per week).

What the systematic review seems to have shown is that there is not yet any strong evidence that Vitamin C can help, regardless of dose, dose frequency or mode of administration.

More studies could very easily change this.