Prevalence of Hepatitis C Among Injection

Drug Users in England and Wales:

 Is Harm Reduction Working?

American Journal of Public Health 39

January 2001, Vol. 91, No.1

American Journal of Public Health 39

 

 

 

Abstract

Objectives: This study sought to establish the prevalence of hepatitis C antibodies (anti-Hepatitis C Virus) and hepatitis B antibodies (anti-HBc) among injection drug users in England and Wales.

Methods: A voluntary cross-sectional survey collected oral fluid samples and behavioral information; 2203 injectors were recruited through drug agencies, and 758 were recruited in the community.

Results: Prevalence was 30% for anti-Hepatitis C Virus, 21% for anti-HBc), and 0.9% for HIV antibodies, Anti-Hepatitis C Virus prevalence rates were significantly greater among those with longer injecting careers, those in older age groups, those residing in London, those recruited in drug agencies, those positive for anti-HBc, and those with a previous voluntary HIV test.

Conclusions: Anti-Hepatitis C Virus prevalence rates among injectors in England and Wales, where comprehensive harm reduction programs exist, are lower than rates in other industrialized countries.  (Am J Public Health.  2001; 91: 38-42)

 

Vivian D. Hope, PhD, MMedSc, Ali Judd, MSc, Matthew Hickman, MPH,

MFPHM(Hon), Theresa Lamagni, MSc, Gillian Hunter; MSc,

Gerry J: Stimson, PhD, MFPHM(Hon), Steve Jones, EA, Linda Donovan, BSc,

John J: Parry, PhD, and 0. Noel Gill, ME, FFPHM

 

 

We conducted a large national cross- sectional study to establish the prevalence of antibodies to Hepatitis C Virus (anti-Hepatitis C Virus) in current injection drug users In the industrialized world, most trans- mission of hepatitis C virus (Hepatitis C Virus) occurs through injection drug use, with prevalence typically above 60% among injection drug users.^I-5 In England and Wales, local studies of injectors receiving drug treatment in the mid-1990s revealed Hepatitis C Virus prevalence of 59% to 67%.^6--8 Estimates of Hepatitis C Virus incidence among injection drug users in other industrialized countries are also high, typically ranging from 10% to 20% per annum.1 For many, infection may be acquired rapidly after initiation of in- jecting⁹; high prevalence has been found

among those with short injecting careers ( e.g., in Baltimore, 65% of those injecting for 1 year or less).10

There is evidence that harm reduction interventions, which include a range of specialized treatment services offering prescription and nonprescription programs as well as needle exchange, have been effective in reducing transmission of HIV among injection drug users.^14-17    Areas that introduced comprehensive harm reduction interventions for injection drug users a decade ago currently have either a low and stable HIV prevalence, as in Australia and the United Kingdom,^I4-17 or a falling prevalence, as in Geneva, Switzerland.18 Transmission of hepatitis B virus (HBV) has also declined in these areas. ^17,!8 There has, however, been little direct evidence indicating that these measures reduce transmission of Hepatitis C Virus ^19,20

Methods

Complementary voluntary unlinked- anonymous surveys of drug users who had injected in the previous 4 weeks were con- ducted at drug agencies (organizations, both public and private, that provide services such as treatment, needle exchange, and ad- vice to drug users) and in the community. Those agreeing to participate provided an oral fluid specimen and completed a brief questionnaire.

As part of an HIV prevalence monitoring program, all injectors in contact with 47 representative drug agencies in England and Wales during 1998 were eligible for inclusion. The methodology has been described elsewhere. ¹⁷ Briefly, agency staff offered participation to all of their injecting clients during the year; those who had not injected in the previous 4 weeks were excluded from the present analysis.

A community survey of injection drug users not receiving specialized treatment for their drug use was conducted in 7 English cities between October 1997 and June 1998 as part of a study of injecting risk behavior!¹ Participants were eligible for the study if they had both injected and not received specialized treatment or had contact with a drug worker in the previous 4 weeks. Recruitment and interviews occurred in a variety of sites, including street locations, social venues, and participants , homes.

Comparable data collected included age, sex, age at first injection, previous voluntary confidential HIV test history, area of recruitment, frequency of sharing injecting equipment ("During the last 4 weeks, how often have you shared injecting equipment?"), and number of sharing partners. The Injecting Risk Questionnaire²² was used in collecting sharing data.

Oral fluid specimens were obtained with the EpiScreen device (Epitope, Inc, Beaverton, Ore) and tested for antibodies to HIV (anti-HIV), to HBV core antigen (anti-HBc), and to Hepatitis C Virus Details on laboratory methods have been published elsewhere²³; specimens that were re- active on initial testing were subjected to confirmatory testing via alternative methods.

Associations between antibody prevalence and covariates were explored in univariate analyses and, subsequently, in a multivariable logistic regression model. In this model, significance was assessed with the likelihood ratio statistic; Stata 6.0 (Stata Corp, College Station, Tex) was used in these analyses.

Incidence rates were estimated among those who had been injecting for less than 2 years. Among those who had been injecting for up to I year, the average injecting career was assumed to be 0.5 years; similarly, for those who had been injecting between I and 2 years, the average injecting career was assumed to be 1.5 years. Those who were anti- Hepatitis C Virus positive were assumed to have been infected at 0.25 and 0.75 years of injecting, respectively.

Results

A total of 2961 participants provided oral fluid samples and completed questionnaires. Of these individuals, 2203 were recruited through drug agencies, and 758 were recruited in the community.

The agency- and community-recruited participants had similar distributions of age and years injecting (Table 1) Overall, 29% were younger than 25 years, and 46% had injected for less than 6 ~. Agency-recruited injectors were less likely to be female or to have been recruited in London {Table I ). Similar proportions in the agency and community groups reported sharing injecting equipment in the previous month and having had a voluntary confidential HIV test {Table I ).

The prevalence of anti-Hepatitis C Virus was 30% {895/2943), and the prevalence of anti-HBc was 21% {616/2955). Table 2 shows the prevalence of anti-Hepatitis C Virus and anti-HBc by different risk factors. Further analysis of risk factors for HIV infection was precluded by the low prevalence of anti-HIV {less than 1%).

Anti-Hepatitis C Virus prevalence increased from 7% among those injecting for less than 3 years to 62% for those who had been injecting for 15 years or more. In comparison with those who had injected for less than 3 years, the adjusted odds ratios of having anti-Hepatitis C Virus were just over 3 for those who had injected for 6 to 8 years and above 7 for those who had injected for 15 or more years (X2s= 120.8, P< .001; Table 2).

The association between age and anti- Hepatitis C Virus prevalence was weaker but still statistically significant, with an odds ratio above 2 for anti-Hepatitis C Virus in those 30 years or older relative to those younger than 20 years (X26= 15.6, P< .02). Anti-Hepatitis C Virus prevalence was elevated in participants who had undergone a previous voluntary confidential HIV test, in those recruited in London, and in those recruited at drug agencies (Table 2).

Prevalence of anti-HBc increased from 5% in those injecting for less than 3 years to 52% in those injecting for 15 or more years. In comparison with those injecting for less than 3 years, the adjusted odds ratios for the presence of anti-HBc were 6.5 among those injecting for 15 or more years and above 2 among those injecting 6 to 8 years (X2s= 103.8, P< .00 I; see Table 2). Anti-HBc prevalence in- creased with increasing age; the odds ratio for anti-HBc was above 2 in those 40 years and older in comparison with those younger than 20 years (X26 = 32.7 , P< .00 1 ). Having undergone a previous voluntary confidential HIV test was positively associated with anti-HBc, but area and site of recruitment were not.

Previous HBV infection was associated with Hepatitis C Virus infection (Table 2); 59% (363/612) of those with anti-HBc also had anti-Hepatitis C Virus; compared with only 23% of those without anti- HBc (X21 = 50.1, P< .00 1 ). Frequency of sharing injecting equipment in the 4 weeks before participation (42%) was not associated with either anti-Hepatitis C Virus or anti-HBc prevalence.

The annual incidence of Hepatitis C Virus infection was estimated to be 4.6% in those who had injected for less than 2 years (23 infections in 502.8 years of exposure ), among whom the anti-Hepatitis C Virus prevalence was 4.~/o(23/471). The equivalent annual incidence for HBV infection was 3.6%, with an anti-HBc prevalence in this group of3.8%.

TABLE 1-Characteristics of Agency- and Community-Recruited Injection Drug Users: England and Wales, 1997-1998
	Agency- Recruited, No. (%) (n=2203)		Community- Recruited. No. (%) (n= 758)		X2	p
Age, y <25 25-29 30-34 >35 Total Gender Female Male Total Number of years injecting     0-2 3-5 6-8 9-11 12-14 > 15 Total Shared injecting equipment in previous month No Yes Total Previous voluntary confidential HIV test No Yes Total Area of recruitment London Elsewhere Total	633  558  503  509 2203     476 1716 2192       557 444 293 224 204 423 2145           1148   833  1981         1016 1092 2108         356 1847 2203	(29) (25) (23) (23)     (22) (78)       (26) (21) (14) (10) (10) (20)	232 194 160 171 757   220 535 755     198 131 109  82  72 145 737         426 328 754       361 395 756     244 514 758	(31) (26) (21) (23)     (29) (71)       (27) (18) (15) (11) (10) (20)           (56) (44)         (48) (52)       (32) (68)	1.5       17.2               3.3               0.5           0.0       89.7	.679       <.001               .653               .492           .833       <.001

Discussion

At 30%, the prevalence of anti-Hepatitis C Virus found in this study was much lower than that found in previous studies. Among those who had been injecting for less than 3 years, the prevalence was 7.4%, and the estimated annual incidence in those who had begun injecting in the previous 2 years was below 5%. These results differ from other evidence suggesting that Hepatitis C Virus infection in injection drug users is Hepatitis C Virus infection in injection drug users is difficult to prevent and that infection is acquired rapidly after initiation into injecting.^9-10

The reliability of the oral fluid tests used is important in assessing our study's results. Ongoing assessment suggests sensitivity and specificity rates of 80% and 99%, respectively, for anti-Hepatitis C Virus and 82%

  and 99%, respectively, for anti-HBc.²³ An evaluation of a similar technique in Scotland showed that anti-Hepatitis C Virus was present in the oral fluid of 85% of 115 injection drug users with serum antibodies to Hepatitis C Virus.²⁴ Adjusting for a test sensitivity of 80% would increase the overall anti-Hepatitis C Virus prevalence to 38% and result in an estimated incidence among recent initiates of 5.7%, but these figures are still lower than what would be expected on the basis of previous studies. Such an adjustment for low test sensitivity would leave unchanged the relative differences in anti-Hepatitis C Virus prevalence according to duration of injection and age.

The illegality of injection drug use, its rarity in the population overall, and the marginalization of injection drug users combine to make monitoring of blood-borne virus trans- mission in this group difficult. Although injectors can be recruited and followed up while receiving treatment²⁵ such interventions are completed by only a subset of participants who tend to be older and to have longer injection drug use careers, which in turn may make their infection incidence rates unrepresentative. The most useful and "representative" data from which inferences about transmission trends can be drawn are probably those provided by large voluntary, unlinked-anonymous cross-sectional surveys of injectors recruited concurrently from drug services and community sites, as we have described here.

Two other studies provide further evidence of a low anti-Hepatitis C Virus prevalence among injectors in England and Wales. First, a 1997-1998 survey of prison inmates reported an anti-Hepatitis C Virus prevalence of 30% among more than 800 prisoners who reported ever injecting drugs.²⁶   Second, an unlinked-anonymous survey involving syphilis serology specimens from more than 1300 injection drug users attending genitourinary medicine clinics during 1995- 1996 revealed an anti-Hepatitis C Virus prevalence rate of 37% (K. Balogun, written communication, August 1999). Once adjusted for test sensitivity, the results of the oral fluid surveys were the same as in this serum survey.

Moreover, the anti-HIV and anti-HBc prevalence in our survey was consistent with earlier data from surveys of injectors recruited drug service and community settings.^15-17  Previous studies in England and Wales may have led to overestimation of the overall prevalence of anti-Hepatitis C Virus because they recruited individuals receiving diagnostic tests while at- tending drug treatment agencies, and these respondents tended to be older and to have had long injecting careers.

Our findings suggest that the prevalence of Hepatitis C Virus infection among injection drug users in England and Wales is lower than that in other industrialized countries.¹  They also suggest that transmission of Hepatitis C Virus among injection drug users in England and Wales may have been reduced in recent years. We may be observing an "aging cohort" effect in the age-specific prevalence of anti-Hepatitis C Virus similar to that observed for anti-HBc following the large decrease in hepatitis B transmission in the mid-1980s²⁷ The possibility of a similar decline in Hepatitis C Virus transmission among injection drug users in Geneva, Switzerland¹⁸; Victoria, Australia²⁸; and Scotland²⁹-albeit against a background prevalence in excess of 50%---has been suggested.

Cross-sectional surveys such as ours, however, cannot provide proof that prevalence and estimated incidence have decreased, establish when such a decrease occurred, or monitor whether the decline is continuing. It is essential, therefore, that prevalence and incidence of anti-Hepatitis C Virus in injectors with short injecting careers be monitored for a number of years.

Cohort studies of the effects on Hepatitis C Virus incidence of individual harm reduction activities, such as needle exchange programs, have produced inconclusive findings;^30-32 but these evaluations of individual prevention measures would not have revealed possible synergistic benefits from large-scale programs consisting of a variety of harm reduction activities. In the United Kingdom, an extensive program that includes widespread access to drug treatment services has existed for many years. An estimated 25 million syringes were distributed in the United Kingdom in 1997, a total that may be higher than that for the United States (J Parsons, verbal communication, August 1999).

The public health success in England and Wales with regard to controlling HIV in injection drug users may have engendered complacency, and opportunities to control Hepatitis C Virus transmission through intensifying harm reduction possibly are being missed. Evidence from HIV research^l2 suggests that increased investment in comprehensive provision of harm reduction interventions may be rewarded with a decrease in Hepatitis C Virus transmission.

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