Limiting re-infection with hepatitis C in people who use
drugs is most likely to be achieved by intensifying provision of sterile
injecting equipment for people using needle and syringe programmes and increasing the number of people who inject drugs who are treated, rather than withholding treatment for people who inject drugs until they stop injecting, a Scottish study suggests.
The study looked at rates of re-infection according to a
person’s pathway to treatment in the Tayside region of Scotland. The region has
a high prevalence of hepatitis C and efforts to eliminate hepatitis C have used
multiple pathways to reach people with testing and treatment services.
People in Tayside may have been diagnosed and treated
through one of six pathways: community pharmacies, drug treatment centres,
prisons, injection equipment provision sites, nurse-led outreach services or
hospital outpatient clinics.
People diagnosed and treated through these pathways are
likely to have different risks of hepatitis C exposure after being cured of
hepatitis C. People using injection equipment provision sites are more likely
to be injecting drugs than people who had been diagnosed and treated through
drug treatment services, for example.
University of Dundee researchers wanted to find out if the
risk of re-infection varied according to treatment pathway, in order to provide
evidence on where to target resources for prevention of re-infection.
They identified everyone treated for hepatitis C and cured
in Tayside between 1998 and 2018, excluding people without follow-up hepatitis
C RNA tests after achieving a sustained virologic response. The analysis was
confined to people with a history of injecting drug use and excluded people
with other risk factors such as exposure to blood products.
The study population comprised 816 people who were not re-infected
after treatment and 100 people who acquired hepatitis C after being cured, a
re-infection incidence of 5.27 per 100 person-years of follow-up.
People who became re-infected with hepatitis C were younger
(40 years vs 47 years). There was no significant difference in the probability
of re-infection between people treated with interferon-based regimens (60% of
the study population) and people treated with direct-acting antivirals (4.93 vs
7.17 per 100 person-years) in a Kaplan-Meier survival analysis (p=0.84).
Kaplan-Meier survival analysis also showed that the risk of
re-infection was greatest in the first 12 months after treatment.
The incidence of re-infection was lowest in people treated
through the hospital outpatient clinic (1.81 per 100 PYs). Rates of
re-infection ranged from 3.13 per 100 PYs in those treated through drug
treatment outreach clinics, 6.39 per 100 PYs in those treated through nurse-led
outreach clinics and 8.14 per 100 PYs in those treated in prison, to 12.12 per
100 PYs in those treated through community pharmacies. The highest rate of
re-infection was observed in people treated through injection equipment
provision sites (19.89 per 100 PYs).
The study investigators say that the high rate of
re-infection observed in people treated through the injection equipment
provision sites might partly be explained by more frequent hepatitis C RNA testing.
Nevertheless, they say their results suggest that resources should be targeted
at injection equipment provision sites to prevent re-infections. Opioid substitution
therapy and high coverage needle and syringe programmes are likely to prevent
a proportion of re-infections but reducing community viral load by increasing the
number of people who inject drugs who are treated and cured will also be
essential to prevent re-infection.
The study investigators also note that when comparing rates of re-infection between cohorts, it is important to pay attention to definitions of injecting drug use. The risk of re-infection may be much lower in people who are receiving opioid substitution therapy and who have injected infrequently in the preceding six months when compared to people who are injecting drugs on a daily basis.