There have been 2 large trials that have compared the effectiveness of pegylated interferon and ribavirin (against alpha interferon with ribavirin), with over 1000 people taking part in each, one conducted by Manns et al and the other by Fried et al. Both reported their results in 2002.
| Pegylated interferon with ribavirin |
| Percentage with no detectable virus 6 months after the end of treatment |
| | Manns | | Fried |
| Overall result | | 54%* | | 56% |
| Genotype 1** | | 42% | | 46% |
| Genotype 2 or 3 | | 82% | | 76% |
| Genotype 4 | | | | 77% |
| Genotype 4, 5 or 6 | | 50% | | |
*Better results (61%) were achieved in a smaller subset of this trial (188 out of the total of 1530 who took part) whose ribavirin dosage was varied according to their weight.
**Note that more recent trials have produced figures of around 50% for genotype 1
Effectiveness of pegylated interferon by itself (monotherapy)
Some people cannot tolerate ribavirin, in particular because it can cause anaemia. For them monotherapy treatment with interferon by itself is the only option. This is not nearly as successful as combination therapy. The results below are from 4 trials, by Heathcote et al, Zeuzem et al, Lindsay et al and Reddy et al, that assessed the effectiveness of pegylated interferon (against alpha interferon).
| Pegylated interferon |
| Percentage with no detectable virus 6 months after the end of treatment |
| Heathcote | Zeuzem | Lindsay | Reddy |
| Overall result | 30%* | 39% | 23% | 36% |
| Genotype 1 | 12% | | 14% | 31% |
| Genotype other than 1 | 51% | | | 50% |
| Genotype 2 or 3 | | | 49% | |
| Genotype 4, 5 or 6 | | | 60% | |
This trial involved only cirrhotics and near-cirrhotics (with scores of 3 or 4 on the Metavir 0 to 4 scale), who typically respond worse to treatment.
