Rectal Treatment Study (RTS)

Project Details

Rectal chlamydia is the most common bacterial sexually transmitted infection (STI) among gay and bisexual men, with prevalence doubling in the last decade from 4% to 8%. Increased uptake of biomedical prevention interventions such as pre-exposure prophylaxis for HIV is reducing condom use and will lead to further increases in rectal chlamydia infections. Rectal chlamydia may exist for long periods without symptoms leading to ongoing transmission; it is associated with HIV.

Azithromycin (1 gram single dose) or 7 days doxycycline (100mg twice daily) are the two recommended treatments with azithromycin as the preferred treatment for chlamydia because of its high adherence (single dose vs 7 day regimen for doxycycline). However, there is increasing concern that single dose azithromycin may be less efficacious than doxycycline for rectal infection in particular, but there has never been a randomised controlled trial (RCT) comparing these treatments for rectal infection, with biologically plausible reasons why azithromycin may be less effective for rectal infection.

This project will generate the first RCT evidence of the efficacy of azithromycin versus doxycycline for the treatment of rectal chlamydia. A double blind RCT will compare the efficacy of 1g dose of azithromycin with doxycycline 100mg twice daily for 7 days among 700 gay and bisexual men attending participating STI clinics. The results will inform chlamydia treatment guidelines in Australia and worldwide.


Prof Jane S Hocking - Lead investigator

Prof Christopher K Fairley

Dr Fabian Kong - co-investigator

Andrew Lau - co-investigator and project co-ordinator

A/Prof Catriona Bradshaw - clinical advisor

A/Prof Marcus Chen - clinical advisor

Dr Natalie Carvalho - health economist


A/Prof Anna McNulty, Site invesitgator (Sydney Sexual Health Centre)
A/Prof David Templeton, Site investigator (RPA Sexual Health)
Prof David Lewis, Site investigator (Western Sydney Sexual Health Centre)
Dr Carol Khaw, Site investigator (Clinic 275)
Dr Mahesh Ratnayake, Site investigator (Clinic 275)
Prof Janaki Amin (Macquarie University)
Prof Basil Donovan (Kirby Institute, UNSW)
Prof Matthew Law (Kirby Institute, UNSW)
A/Prof Sepehr Tabrizi (Kirby Institute, UNSW)
Prof Mark Boyd (University of Adelaide)
Prof Peter Timms (University of Sunshine Coast)
A/Prof David Regan (Kirby Institute, UNSW)
Prof John Kaldor (Kirby Institute, UNSW)
Dr Lenka Vodstrcil (Monash University)

Melbourne Sexual Health Centre

Western Sydney Sexual Health Centre (WSSHC)

RPA Sexual Health

Clinic 275

The Kirby Institute

The University of the Sunshine Coast


National Health and Medical Research Council (NHMRC)

Research Publications

Lau A, Kong F, Fairley CK, Donovan B, Chen M, Bradshaw C, Boyd M, Amin J, Timms P, Tabrizi S et al: Treatment efficacy of azithromycin 1 g single dose versus doxycycline 100 mg twice daily for 7 days for the treatment of rectal chlamydia among men who have sex with men - a double-blind randomised controlled trial protocol. BMC Infect Dis 2017, 17(1):35

Lau, Andrew MSc; Kong, Fabian Y.S. PhD; Fairley, Christopher K. PhD; Templeton, David J. PhD; Amin, Janaki PhD§; Boyd, Mark A. MD; Bradshaw, Catriona PhD; Chen, Marcus Y. PhD; Donovan, Basil PhD; Khaw, Carole MD∗∗; Lewis, David A. FRCP(UK), PhD††; McNulty, Anna PhD‡‡; Regan, David G. PhD; Ratnayake, Mahesh MD∗∗; Hocking, Jane S. PhD§§; On behalf of all RTS investigators: Factors Associated With Early Resumption of Condomless Anal Sex Among Men Who Have Sex With Men After Rectal Chlamydia Treatment

Andrew Lau, M.S., Fabian Y.S. Kong, Ph.D., Christopher K. Fairley, Ph.D., David J. Templeton, Ph.D., Janaki Amin, Ph.D., Samuel Phillips, Ph.D., Matthew Law, Ph.D., Marcus Y. Chen, Ph.D., Catriona S. Bradshaw, Ph.D., Basil Donovan, M.D., Anna McNulty, M.D., Mark A. Boyd, M.D., et al: Azithromycin or Doxycycline for Asymptomatic Rectal Chlamydia trachomatis.June 24, 2021 N Engl J Med 2021; 384:2418-2427 DOI: 10.1056/NEJMoa2031631

Research Group

Sexual Health

Faculty Research Themes

Infection and Immunology

School Research Themes

Disparities, disadvantage and effective health care, Screening and early detection of disease

Key Contact

For further information about this research, please contact the research group leader.

Department / Centre

Centre for Epidemiology and Biostatistics

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