Rachel Sacks-Davis
Doctor Campbell Aitken, Doctor Jason Grebely, Professor Margaret Hellard
Globally, approximately 180 million people are infected with hepatitis C virus (HCV), with an estimated three to four million new infections each year. In the developed world, the primary at-risk population for HCV infection are people who inject drugs (PWID), with 86% of new infections in Australia attributed to injecting drug use. Although Australian harm reduction programs successfully prevented an HIV epidemic amongst PWID, current prevention programs have not been successful in reducing hepatitis C transmission. Whilst some risk factors for infection with HCV are well established – for example, length of injecting career and injecting with used needles – results vary considerably between studies both around rates of primary infection, reinfection, and clearance and predictors. A more detailed exploration of social and behavioural factors influencing risk of disease transmission and progression will inform future public health programs, and a more detailed exploration of biological factors – for example, host genetics and immunity – will inform vaccine development.
To identify behavioural, social, virus and host factor determinants of hepatitis C primary infection, reinfection, and spontaneous clearance.
This research uses data from the Networks 2 study - a cohort of injecting drug users based in Melbourne, Australia, and recruited using a social network design - and an international collaboration of cohort studies of hepatitis C in injecting drug users, InC3. Traditional analytic methods are combined with mathematical modelling. A systematic review of existing literature was also undertaken.
A systematic review was undertaken of behavioural interventions for preventing hepatitis C transmission in people who inject drugs. Six trials evaluating peer-education training and counselling interventions were included in the review. Behavioural interventions were defined as nonpharmacological interventions that aimed to change individual behaviours without explicitly attempting to change population norms. There was considerable variation in study design, outcome measures and magnitude, direction and statistical significance of findings between studies. Nonetheless, results suggested that it is unlikely that behavioural interventions alone can have a considerable effect on HCV transmission. It is likely that multi-component interventions are required.
In addition to individual risk factors such as age, gender, frequency of injecting drug use and other injecting-related risk behaviours, it is hypothesized that social network factors affect hepatitis C transmission. Social network factors include the number of injecting partners and their characteristics, as well as the overall structure of the social-injecting network. We would expect that there would be close concordance between the social-injecting network of people who inject drugs and the pattern of genetic relatedness of their hepatitis C infections; however, previous studies have not identified such a relationship. Through an analysis of data from the Networks 2 study, we were able to show that that the pattern of genetic relatedness of hepatitis C infection was associated with the social-injecting network. Our findings highlight the importance of investigating social network factors in studies of hepatitis C transmission, and raise the possibility of using social network methods in public health interventions aimed at reducing hepatitis C transmission risk. For example, injecting relationships may be effective pathways for communicating information about safe-injecting practices, and it may be possible to develop public health interventions targeted at injecting partners or groups rather than individuals.
R Sacks-Davis, E McBryde, J Grebely, M Hellard, P Vickerman. Most hepatitis C reinfections that clear spontaneously go undetected – Bayesian analysis of a prospective longitudinal study. The 8th Australasian Viral Hepatitis C Conference. Auckland, September 2012.
R Sacks-Davis, E McBryde, J Grebely, M Hellard, P Vickerman. 2012. Mathematical modelling of observational study data suggests high underlying rates of reinfection and spontaneous clearance. 14th International Symposium on Viral Hepatitis and liver Disease. Shanghai, June [poster].
R Sacks-Davis, E McBryde, J Grebely, M Hellard, P Vickerman. Projecting probable missing hepatitis C reinfection data given a set of observations and intervals between study visits. The RC33 8th International Conference on Social Science Methodology, Sydney, July 8-13, 2012.
R Sacks-Davis, G Daraganova, C Aitken, P Higgs, R Jenkinson, L Tracy, D Bowden, G Robins, P Pattison, J Grebely, A Barry, M Hellard. Hepatitis C Transmission in a Social Network of People who Inject Drugs. The International Sunbelt Social Network Conference, Redondo Beach, March. 2012
Sacks-Davis R, Aitken C, Higgs P, Spelman T, Pedrana A, Bowden D, Bharadwaj M, Nivarthi U, George J, Drummer H, Hellard M. 2011. Hepatitis C clearance and reinfection in a cohort of people who inject drugs: behavioural and genetic correlates. AASLD San Francisco November 2011 [poster].
R Sacks-Davis, D Horyniak, J Grebely, M Hellard. Behavioural interventions for preventing hepatitis C infection in injecting drug users - a systematic review and meta-analysis. IHRA 22nd International Conference, Beirut: April 3-7 2011
R Sacks-Davis, C Aitken, P Higgs, T Spelman, A Pedrana, D Bowden, M Bharadwaj, U Nivarthi, V Suppiah, J George, H Drummer, M Hellard. Hepatitis C reinfection and clearance in a cohort of people who inject drugs. 2nd International Symposium on Hepatitis care in substance users, Brussels: September 15-16, 2011
Sacks-Davis, R., Higgs, P., Aitken, C., Dowden, S., Tracy, L., Bharadwaj, M., & Hellard, M. 2011. Detailed contact data are important to distinguish HCV resurgence and reinfection, 2nd International Symposium on Hepatitis care in substance users, Brussels: September 15-16 [poster].
Sacks-Davis, R., Daraganovo, G., Aitken, C., Higgs, P., Tracy, L., Bowden, D., Robins, G., Pattison, P., Grebely, J., Barry, A., & Hellard, M. 2011.The molecular epidemiology of hepatitis C and social network research provide insights into transmission pathways for people who inject drugs, 2nd International Symposium on Hepatitis care in substance users, Brussels: September 15-16 [poster].
R. Sacks-Davis, G. Daraganova, C. Aitken, P. Higgs, L. Tracy, D. Bowden, G. Robins, P. Pattison, J. Grebely, A. Barry, M. Hellard. “Molecular epidemiology of hepatitis C in a social network of young people who inject drugs.” 46th Annual Meeting of the European Association for the Study of the Liver (EASL), Berlin, March-April 2011 [poster].
R. Sacks-Davis, C. Aitken, P. Higgs, S. Moneer, J. Flynn, V. Suppiah, L. Tracy, R. Ffrench, D. Bowden, H. Drummer, J. George, M. Bharadwaj, M. Hellard. “Hepatitis C virus-specific cellular immunity does not protect against future HCV infection in anti-HCV negative injecting drug users.” 46th Annual Meeting of the European Association for the Study of the Liver (EASL), Berlin, March-April 2011 [poster].
R Sacks-Davis, CK Aitken, P Higgs, S Moneer, J Flynn, V Suppiah, L Tracy, R Ffrench, J George, D Bowden, H Drummer, M Bharadwaj, ME Hellard. ELISpot testing shows very few people who inject drugs avoid hepatitis C exposure. 7th Australasian Viral Hepatitis Conference, Melbourne, September 2010.
Sacks-Davis R, Horyniak D, Grebely J, Hellard M. Behavioural interventions for preventing hepatitis C infection in people who inject drugs: A global systematic review. International Journal of Drug Policy 2012; 23:176-184 DOI: 10.1016/j.drugpo.2011.08.002. IF(2010): 2.763
Sacks-Davis R, Van Gemert C, Bergeri I, Stoove M, Hellard M (2012) Identifying newly acquired cases of hepatitis C using surveillance: a literature review. Epidemiology and Infection 140:1925-34. doi:10.1017/S0950268812001033. IF(2010): 2.318
Sacks-Davis R, Daraganova G, Aitken C, Higgs P, Tracy L, et al. (2012) Hepatitis C Virus Phylogenetic Clustering Is Associated with the Social-Injecting Network in a Cohort of People Who Inject Drugs. PLoS ONE 7(10): e47335. doi:10.1371/journal.pone.0047335 IF(2010): 4.610
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