Protecting against sexually transmitted infections (STIs)

• What are sexually transmitted infections (STIs)?
• Who gets STIs?
• Predisposing factors of STIs
• How are STIs prevented?
  • Biomedical approaches to STI prevention
    • Male condom
    • Female condom
    • Male circumcision
    • Vaccination
    • STI treatment
    • Contact tracing
    • Screening
  • Behavioural approaches to STI prevention
  • Structural approaches to STI prevention

What are sexually transmitted infections (STIs)?

Sexually transmitted infections (STIs), as the name suggests, are a group of bacteria and viruses which can be, and most commonly are, transmitted through sexual contact, including vaginal, anal and oral sex. Many STIs also spread through other means (e.g. blood transmission).
As a group of diseases, the infections are extremely varied. For example, some STIs result in symptoms such as genital discharges or abnormal growths in the genital area (e.g. herpes); some usually have no symptoms (e.g. chlamydia); and others have no apparent effect on the body but create a pathway for other deadly diseases to occur. Human immunodeficiency virus (HIV) is the causal agent of acquired immune deficiency syndrome (AIDS).
Some of the most commonly occurring STIs, and those which are a considerable health concern in Australia, include:

• Human immunodeficiency virus (HIV): HIV is a retrovirus transmitted through blood, breast milk and sexual fluids. It leads to AIDS, an immune deficiency syndrome for which there is no cure. HIV typically remains dormant for many years before AIDS develops (e.g. ten years). Individuals who become infected with HIV ultimately die of coexisting infections following the onset of immune deficiency.
• Human papilloma virus (HPV): HPV is an STI that causes warts on the genitals and other sites. It is often asymptomatic (but contagious) for considerable periods of time. Specific subtypes of the virus are the causal agents in cervical and anal cancer.
• Herpes simplex virus (HSV): There are two types of HSV: type 1 and type 2. They cause the condition commonly known as genital herpes, characterised by lesions on the genitals, and/or sores and blisters around the mouth. The symptoms of the disease are easily treatable, but once infected with herpes simplex, individuals will carry the virus throughout their lives and symptomatic outbreaks may occur periodically.
• Hepatitis B: Heptatis B virus affects liver function and typically leads to either acute or chronic inflammation of the liver. While the disease can be sexually transmitted, evidence suggests that in Australia it is most commonly acquired through intravenous drug use.
• Chlamydia: Chlamydia is the most commonly occurring STI in Australia, and the most commonly reported of all notifiable infections in Australia. It is caused by the bacteria Chlamydia trachomatis. Although it is often asymptomatic, it may also lead to genital infections (e.g. pelvic inflammatory disease), and discharges and blindness in neonates born to women with asymptomatic chlamydia. Infertility can result if chlamydia is left untreated in women.
• Gonorrhoea: Gonorrhoea is a bacterial infection of Neisseria gonorrhoea. It typically causes genital infections (e.g. pelvic inflammatory disease) and discharges. If left untreated, it can cause infertility in women and increases the risk of pregnancy complications (e.g. ectopic pregnancy).
• Syphilis: Syphilis is a bacterial infection caused by Treponema pallidum. It sometimes remains asymptomatic, but can also result in genital lesions, ulcers and discharges. The infection typically goes through infectious and non-infectious stages, in which symptoms resolve as the bacteria lie dormant. Syphilis is primarily transmitted sexually; it can also be transmitted from a pregnant woman to her foetus during pregnancy. Untreated syphilis can result in serious neurological and cardiovascular disorders, and can also have a severe impact on the developing foetus if transmitted during pregnancy.
• Trichomoniasis: Trichomoniasis is a bacterial infestation of Trichomonas vaginalis organisms that affects women. It typically results in a yellow/green frothy discharge, though it can also be asymptomatic.

Who gets STIs?

Globally, there are large differences in the incidence and prevalence of STIs. For example, in parts of southern Africa where STIs are very common, the prevalence of HIV is as high as 25% (amongst 16–59 years olds), and up to 19% of all pregnant women are carriers of other STIs (e.g. syphilis, chlamydia). Infection rates are much lower in Australia, but STIs remain a considerable public health burden, despite the availability of effective methods to prevent and treat many conditions. Evidence suggests that the incidence of a number of STIs has risen in recent years.
There is considerable variation in the incidence of particular STIs in Australia:

• HIV: 1,051 new cases of HIV were diagnosed in Australia in 2007. The annual incidence of HIV has increased by almost 50% since 1999, when 718 new cases were diagnosed. It is estimated that 85% of incident cases of HIV are diagnosed in homosexually active men. The estimated number of people currently living with HIV infection in Australia is 16,692.
• HPV: The most common sexually transmissible infection in developed countries. There is no data regarding the incidence of HPV in Australia, as it is not a notifiable infection.
• HSV: 2.1% of Australian men and 2.5% of women reported experiencing genital herpes at some point in their life to the Sex in Australia survey. The annual prevalence is estimated at 0.8% for men and 1.1% for women.
• Hepatitis B: 0.7% of Australian men and women reported infection with the hepatitis B virus at some point in their life. The annual incidence is less than 0.1%. Evidence suggests that, in Australia, this condition is most commonly transmitted through intravenous drug use and not sexual activity.
• Chlamydia: 51,867 new cases of chlamydia (or 245 cases per 100,000 people) were reported in 2007, making this the most commonly occurring notifiable infection in Australia. The incidence of chlamydia has increased steadily in Australia in the past decade; there was a 7% increase in cases of chlamydia from 2006 to 2007. The Sex in Australia survey reported that 1.7% of male and 3.1% of female respondents had ever experienced chlamydia, while 0.2% of men and women had experienced the disease in the year prior to being surveyed.
• Gonorrhoea: 36.1 cases per 100,000 people were diagnosed with gonorrhoea in 2007. In the Sex in Australia survey, 2.2% of men and 0.6% of women reported having ever had gonorrhoea.
• Syphilis: Around 2,500 cases of syphilis were reported in Australia in 2004 (3.1/100,000). The rate of incident cases more than doubled in 2006–07, when 6.6 cases per 100,000 people were reported. The increase was mainly due to increasing incidence amongst homosexually active men. The Sex in Australia survey reported that 0.6% of male and 0.1% of female respondents had ever experienced syphilis.
• Trichomoniasis: There are no accurate data available regarding the prevalence of trichomoniasis as the disease is not notifiable in Australia, though evidence suggests that the incidence has decreased markedly in recent years. The Sex in Australia survey reported a lifetime prevalence of 0.8% and an annual incidence of less than 0.1% for women.
• Genital warts: Genital warts are a symptom of a range of STIs, including HPV and HSV. 4.0% and 4.4% of Australian men and women respectively reported having genital warts at some time in their life, while 0.5% of men and 0.3% of women reported experiencing warts in the past year.

Predisposing factors of STIs

The prominence of sexually transmitted infections varies depending on the specific infections. However, as a group of infections, particular groups of people (characterised either by demographic or behavioural features) are more likely to experience STIs than others. In Australia, factors which are associated with an increased risk of STIs include:

• Indigenous Australian ethnicity: Rates of STIs reported for Indigenous Australians are significantly higher than for non-Indigenous Australians. In 2004, Indigenous Australians had an 8-fold higher risk of chlamydia, an 80-fold higher risk of gonorrhoea, and a 100-fold greater risk of syphilis.
• Gender: Men are more likely to have experienced STIs than women. The lifetime experience of any STI in men is 20.2%, and for women is 16.9%.
• Sexual orientation: Men who identify as homosexual are more than 6 times more likely to have experienced an STI in their lifetime than men who identify as heterosexual. Amongst women, those who identify as bisexual are more than 3 times more likely to have experienced STIs at some point in the past than their heterosexually identifying counterparts.
• Injecting drug use: Injecting drug use is a risk factor for lifetime and past year experience of STIs. Men and women are roughly three and five times more likely, respectively, to experience an STI if they use intravenous drugs.
• Speaking English at home: Individuals who speak a language other than English at home are half as likely to experience an STI in their lifetime, compared to those who speak English at home.
• Education: Women who attend post secondary education are 1.33 times more likely to experience an STI in their lifetime.
• Working as a sex worker: Both men and women who work in the sex industry have an increased risk of STI. Men are nearly four times more likely, and women nine times more likely, to have ever experienced an STI if they work in the sex industry.
• Paying for sex: Men who pay for sex are over three times more likely to have experienced an STI in their lifetime, and more than twice as likely to have experienced an STI in the past year, than men who have never paid for sex.
• Working in a managerial or professional occupation: Men and women with professional or managerial occupations are 1.25 times more likely to have experienced an STI in their lifetime than their counterparts working in white or blue collar occupations.
• Greater number of sexual partners: Respondents to the Sex in Australia survey who had ever experienced an STI, had, on average, a significantly greater number of sexual partners than respondents who had never experienced an STI (for men, 41.5 vs 12.2; for women, 16.2 vs 5.5). Men and women who have experienced an STI in the past year are three times more likely to have had more than one partner in the previous year.
• Non-use or inconsistent use of condoms: Not using condoms, or using them inconsistently, is an important risk factor for individuals who have sex with multiple partners, or with a single partner who has an STI.
• Age: Young people, particularly those aged 15–24, are more likely to contract STIs than their older counterparts. Of all cases of chlamydia newly diagnosed in Australian women in 2004, 70% were in women younger than 25.
• Imprisonment: Several studies have reported rates of STI in prisoner populations higher than those in the general population. One study reported that 2% of imprisoned men and 1% of women had syphilis. Another reported that some 58% of female inmates were positive for HSV2 antibodies.
• Intimate partner violence: Women who experience intimate partner violence are more likely to contract HIV or another STI. A study of teenage women in America found that those who experienced violence in their intimate relationships were 2.6 times more likely to have been diagnosed with an STI. An Australian survey found that women who experienced partner violence were more likely to have genital herpes than those who did not.

How are STIs prevented?

Preventing STIs is much better than treating them, because when diseases are prevented people do not get sick and do not need to access health services which are expensive to provide. Therefore, developing effective strategies to prevent STIs is of extreme importance to public health.
It is recommended that STI prevention programs take a multi-pronged approach aiming to:

• Reduce the risk of transmission per sexual act;
• Reduce the number of at risk partners; and
• Reduce the period of exposure to STIs.

In practice, this means STI prevention efforts mainly focus on promptly treating curable STIs, notifying the partners of infected individuals, and encouraging safer sexual practices (e.g. condom use).
More recently, interventions have also focused on changing the conditions in which high risk sexual behaviours occur (e.g. situations in which women are poor and therefore have sex in exchange for money).
Developing strategies to effectively prevent STIs has proven challenging. Techniques which are effective in reducing the spread of an STI often contradict an individual’s beliefs regarding what is and is not appropriate sexual behaviour. For example, someone who believes for religious reasons that an individual should not have sex until they get married may disagree with condom distribution as an STI prevention strategy. As such, there has been a tendency for STI prevention programs to focus on promoting the adoption of morally correct sexual behaviours which are unachievable for some and undesirable for many (e.g. long term abstinence) as the best method of STI prevention.
In many cases, abstinence has been promoted at the expense of STI prevention techniques which are biomedically effective. When making decisions about your own sexual health or informing friends or children, it is important to remember that many individuals fail to abstain, and it is therefore necessary that they are aware of other STI prevention techniques.
It is also important to note that many individuals perceive abstinence to mean abstaining from vaginal intercourse. Those who abstain in this manner may be more likely to engage in anal or oral intercourse as alternatives to vaginal intercourse. When discussing abstinence, it must be emphasised that STIs can be passed on during anal and oral intercourse, so abstaining from vaginal intercourse alone is not sufficient for protection.
General practitioners play an important role in treating and screening for STIs (which are important factors in prevention). Prevention programs are conducted by a range of other health professionals and non-professionals, using a range of styles in a range of settings.
In terms of the style of communication used and target audience, STI programs might be referred to as:

• Peer education: Programs in which individuals with similar demographic or other characteristics to the target audience (e.g. youth, sex workers) facilitate educational sessions or access to technologies (e.g. condoms). Individuals are most able to discuss sensitive issues with other like individuals, and are more able to digest and understand educational information provided by a like individual.
• Community based: Programs based within a specific community, usually a community identified as having a high risk of STI (e.g. college students, homosexual men). Community based programs typically aim to involve the target group in program planning and design, and empower them to gain greater control over their health.
• Clinically based: Programs run from health facilities by health professionals. They typically focus on providing biomedical interventions (e.g. vaccinations or treatments).
• Mass media: Programs distribute educational and behavioural messages through the mass media.
• Social marketing: STI prevention technologies (e.g. condoms) are promoted for sale at a subsidised price.

In terms of the issues they address, approaches to STI prevention can be broadly classified as:

• Biomedical
• Behavioural
• Structural

While the approaches can be used separately (e.g. a clinic providing STI treatment only), the greatest effect is achieved by combining the approaches. For example, a clinic which treats STIs (biomedical) may also provide motivational counselling for behaviour change (behavioural) and free condoms to increase their accessibility (structural).

Biomedical approaches

A range of biomedical approaches are effective in preventing a variety of STIs. However, encouraging people to access and use biomedical technologies has proven difficult, and the theoretical efficacy of a biomedical technology has never translated into equal real effectiveness.

Male condom

Male condoms are latex sheaths which are inserted on the erect penis to provide are barrier to sexual fluids during sexual activity. Intact latex is completely impenetrable by sexual fluids, but condoms may break or slip off during sexual activity, and are thus not 100% effective. Breakage and slippage are more likely if the condom is incorrectly applied.
Condoms should be applied to an erect penis before every act of genital contact (e.g. stroking the vagina or anus with the penis) or oral, anal or vaginal sex. The penis should be withdrawn from the vagina or anus immediately after ejaculation, while the penis remains erect. Condoms should also be used in conjunction with water based lubricants (as opposed to oil based lubricants, which interfere with latex) to prevent breakage.
When used correctly, condoms are effective in preventing men and women from contracting HIV, gonorrhoea, chlamydia and trichomoniasis. They are much less effective in protecting against ulcerating genital infections. This is because of the anatomical protection condoms provide (i.e. they only cover the penis and not other genital areas like the scrotum). A condom does not provide a full barrier to the transmission of ulcerating STIs because they are spread by contact between infected skin and mucosal surfaces, unlike other STIs which are transmitted through vaginal fluids and semen.
As an HIV prevention method for heterosexual couples, condoms have been estimated to be 80% effective when used consistently, and 95% effective when used correctly and consistently. Condoms also provide highly effective (98%) contraceptive protection, when used consistently and correctly and thus can also prevent unwanted pregnancy.
For more information, see Male Condom.

Female condoms

Female condoms are polyurethane sheaths which are inserted into the vagina before sexual intercourse. They were developed as a female initiated barrier method for STI prevention, in recognition that decisions about use of male condoms were predominately controlled by men.
Female condoms provide as equally an effective barrier to STIs as male condoms, but have proven no more effective in practice than male condoms. This indicates that females are no more able to initiate or insist on the use of female condoms than male condoms. In addition, female condoms are more expensive to produce, and users are more likely to report mechanical difficulties with female than male condoms.
For more information, see Female Condom.

Male circumcision

Male circumcision is the process of surgically removing a man’s foreskin. It has traditionally been performed for religious and cultural reasons, typically during infancy or adolescence. Recently, evidence from sub-Saharan African countries, where HIV is very common, has shown that circumcision provides men with protection against HIV infection. One randomised controlled trial reported that participants in the intervention group (i.e. those who received the circumcision intervention) were 60% less likely to have contracted HIV in the 18 months following circumcision than individuals in the control group. The study did not examine the risk of other STIs.

Vaccination

Hepatitis B and HPV are both preventable with vaccines. While much research has been focused on finding a vaccine for HIV, a vaccine is unlikely to be available in the foreseeable future.

STI treatment for prevention of curable STIs

Many STIs can be cured easily through the administration of antibiotics. Treating STI carriers eliminates the risk of a carrier’s sexual partner/s contracting the disease. However, individuals who have STIs may not seek treatment, either because they are asymptomatic and unaware of their infection status, or because they find it difficult to go to a health facility for STI treatment (e.g. because they are embarrassed). Identifying STI carriers is thus an important factor in ensuring treatment is received.
Individuals who think they may have been exposed to an STI (e.g. because they had unprotected sex with a casual partner) should not feel embarrassed about visiting a general practitioner to be checked. STIs occur commonly in the general population, so doctors come in to contact with many patients who have STIs, and know how to treat them. Doctors are also able to provide advice about STI prevention to individuals who have questions.

Contact tracing for prevention

Contact tracing is the process of contacting the sexual partners of an individual diagnosed with a STI, so that they can be clinically assessed and treated if they have also been infected. Typically, the STI carrier will play an important role in contact tracing (e.g. by giving each sexual partner a letter from the doctor stating the diagnosis and need for clinical assessment). In cases where the STI carrier is unable or unwilling to trace contacts, general practitioners can refer the case to contact tracers at the local health department.

Screening high risk populations

Many STIs are asymptomatic but diagnosable with simple tests. Doctors sometimes screen patients who they think are at risk of STIs. Risk factors which may prompt a general practitioner to screen for STIs include:

• Age 15–29 years
• History of STI
• Homosexual activity
• Partner with an STI
• Sexual activity overseas
• Indigenous Australian ethnicity
• Sex with a non-regular partner without condom use
• Multiple sexual partners
• Recently changed sexual partner
• Sex workers
• Pregnant women under 25 years of age

Other biomedical approaches

Biomedical technologies which have proven ineffective, or for which insufficient evidence of effectiveness has been produced, include:

• Vaginal microbicides and spermicides: There are currently no antimicrobial or spermicidal products that protect against HIV or other STIs;
• Cervical barriers (e.g. diaphragm): Although these have not been proven to reduce HIV transmission, they have received little attention as an HIV prevention method and are likely to play an important role if a suitable microbicide is developed to prevent HIV or other STIs.

Behavioural approaches

Behavioural approaches to STI prevention focus on motivating individuals to modify behaviours which increase their risk of STI (e.g. increase condom use or reduce number of sexual partners). They may involve communication through peer education, community groups or the mass media, and typically attempt to develop targeted messages appropriate to individuals with high risk behaviours or focusing on specific scenarios in which high risk behaviour is more likely (e.g. intoxication). While a number of behaviour change programs have been successful (including Australia’s campaign to encourage condom use amongst homosexual men), evidence demonstrates that behaviour change is difficult to sustain in the long term.
Behavioural approaches often incorporate a “life skills” component which focuses on developing core sexual communication skills in participants (e.g. negotiation of condom use). Such programs recognise that, despite knowledge of the transmission routes and health effects of STIs and a desire to change behaviour, some individuals are often unsure of how to negotiate with their partners to implement protective behaviours.
Depending on the type of behaviour change they advocate, programs can generally be classified as:

• Abstinence only: Abstinence only programs promote sexual abstinence until marriage as the only 100% effective means of STI prevention, and often withhold information about other prevention strategies. While the message is undoubtedly correct (abstinence is the only 100% effective prevention strategy), abstinence in the long term has proven an unrealistic behaviour for many. As a result, abstinence only programs have failed to have any effect on rates of STIs or on reducing risky behaviours, because program participants are unable or choose not to abstain from sexual activity;
• Abstinence plus (ABC): Abstinence plus programs promote abstinence as the most effective means of STI prevention, and also provide evidence-based information about the effectiveness of condoms, delayed sexual debut and partner reduction as STI prevention strategies. Abstinence plus programs for HIV prevention have not been found to have a protective effect in terms of self-reported STI incidence, but have produced favourable behavioural outcomes (e.g. reduced numbers of sexual partners).
• Consistent condom use: Programs solely promoting the consistent use of condoms tend to focus on groups at a high risk for STIs because of their sexual behaviours (e.g. sex workers, sex-on-site venue visitors). A number of programs have produced successful results in terms of HIV prevention.
• Health facility access: Other behavioural programs focus on motivating individuals to attend health facilities, where they may access diagnostic and treatment services, as well as receive information about STI risk factors and prevention methods.

Structural approaches

Structural factors (i.e. political, economic, social and environmental factors) play an important role in the transmission of STIs because they shape and constrain individuals’ sexual behaviours. Structural approaches to STI prevention aim to alter the conditions in which individuals exist, to make them more favourable to STI prevention. They are most common in developing countries where structures tend to be less conducive to STI prevention (e.g. the status of women is lower, more people live in poverty). Attempts to change structural factors have also been apparent in many STI prevention campaigns in Australia.
Australia’s success in reducing the spread of HIV amongst homosexually active men in the 1980s and 1990s had many structural aspects. Rather than being based on a single intervention (e.g. providing condoms in sex-on-site venues) the campaign was broad-based, involved a range of interventions and, most importantly, was carried out in an environment supporting open discussion of HIV, its risk factors and prevention approaches, and involving social and political mobilisation of the affected group (i.e. homosexually active men).
Other examples of issues which may comprise part of a structural approach to STI prevention include:

• Changing attitudes: A number of HIV prevention programs in southern Africa, where HIV is most highly prevalent, attempt to change male attitudes regarding gender roles and the sexual rights of women.
• Reducing social marginalisation: Individuals who are socially marginalised have a greater risk of STI because their social conditions predispose them to risky sexual behaviours (e.g. there is a high rate of prostitution amongst female intravenous drug users), and make it more difficult for them to access health facilities (e.g. for fear of discrimination). Programs that advocate for the rights of socially marginalised groups can therefore also impact on the sexual risk in such groups.
• Increasing access to preventative technologies: Making condoms more accessible in schools or workplaces, or providing free health care services.

 

More information

For more information on different types of sexually transmitted infections, prevention of STIs, treatments and effects on fertility, see Sexually transmitted infections (STIs).

 

For more information on different types of contraception, male and female anatomy and related health issues, see Contraception.

 

References

1. Sexual Health Society of Victoria. National management guidelines for sexually transmissible infections [online]. Royal Australian College of General Practitioners. 18 December 2008 [cited 29 June 2010]. Available from: URL link
2. Commonwealth of Australia. National sexually transmissible infections strategy 2005-2008 [online]. Australian Government Department of Health and Ageing. 27 June 2005 [cited 10 February 2009]. Available from: URL link 
3. McDonald A [ed]. HIV/AIDS, viral hepatitis and sexually transmissible infections in Australia annual surveillance report 2008 [online]. National Centre in HIV Epidemiology and Clinical Research, University of New South Wales. 30 September 2008 [cited 10 February 2009]. Available from: URL link
4. Jin F, Prestage GP, Kippax SC, Pell CM, Donovan BJ, Kaldor JM, et al. Epidemic syphilis amongst homosexually active men in Sydney. Med J Aust. 2005; 183(4):179-83.
5. Central Statistical Office, Ministry of Economic Planning and Development, Swaziland; Measure DHS. Swaziland demographic and health survey 2006-07 [online]. Southern Africa HIV and AIDS Information Dissemination Service (SAfAIDS). 25 July 2007 [cited 10 February 2009]. Available from: URL link
6. Ministry of Health and Social Welfare, Kingdom of Swaziland. Eighth HIV sentinel serosurveillance survey [online]. Family Health International. 26 December 2002 [cited 10 February 2009]. Available from URL link
7. Grulich AE, de Visser RO, Smith AM, Rissel CE, Richters J. Sex in Australia: Sexually transmissible infection and blood-borne virus history in a representative sample of adults. Aust NZ J Public Health. 2003; 27(2): 234-41.
8. Centers for Disease Control and Prevention. Condoms and STDs: fact sheet for public health personnel [online]. 6 February 2009 [cited 10 February 2009]. Available from URL link
9. Skinner SR, Hickey M. Current priorities for adolescent sexual and reproductive health in Australia. Med J Aust. 2003; 179(3): 158-61.
10. Butler T, Robertson P, Kaldor J, Donovan B. Syphilis in New South Wales (Australia) prisons. Int J STD AIDS. 2001; 12(6): 376-9.
11. Butler T, Donovan B, Taylor J, Cunningham AL, Mindel A, Levy M, et al. Herpes simplex virus type 2 in prisoners, New South Wales, Australia. Int J STD AIDS. 2000; 11(11): 743-7.
12. Decker MR, Silverman JG, Raj A. Dating violence and sexually transmitted disease/HIV testing and diagnosis among adolescent females. Pediatrics 2005; 116(2); e272-6.
13. Khan A, Hussain R, Schofield M. Correlates of sexually transmitted infections in young Australian women. Int J STD AIDS. 2005; 16(7): 482-7.
14. Padian NS, Buvé A, Balkus J, Serwadda D, Cates W Jr. Biomedical interventions to prevent HIV infection: evidence, challenges and way forward. Lancet. 2008; 372(9638): 585-99.
15. Gupta GR, Parkhurst JO, Ogden JA, Aggleton P, Mahal A. Structural approaches to HIV prevention. Lancet. 2008, 372(9640): 764-75.
16. Coates TJ, Richter L, Caceres C. Behavioural strategies to reduce HIV transmission: how to make them work better. Lancet. 2008; 372(9639): 669-84.
17. Pinkerton SD, Abramson PR. Effectiveness of condoms in preventing HIV transmission. Soc Sci Med. 1997; 44(9): 1303-12.
18. Weller S, Davis K. Condom effectiveness in reducing heterosexual HIV transmission. Cochrane Database Syst Rev. 2002; (1): CD003255.
19. Auvert B, Taljaard D, Lagarde E, Sobngwi-Tambekou J, Sitta R, Puren A. Randomized, controlled intervention trial of male circumcision for reduction of HIV infection risk: the ANRS 1265 trial. PLoS Med. 2005; 2(11): e298.
20. Round up Human papillomavirus vaccination. Reprod Health Matters. 2007; 15(29): 193-6.
21. Cheney K, Wray L. Chlamydia and associated factors in an under 20s antenatal population. Aust NZ J Obstet Gynaecol. 2008; 48(1): 40-3.
22. Gray RH, Wawer MJ. Reassessing the hypothesis on STI control for HIV prevention. Lancet. 2008; 371(9630): 2064-5.
23. Harrison PF, Rosenberg Z, Bowcut J. Topical microbicides for disease prevention: status and challenges. Clin Infect Dis. 2003, 36(10): 1290-4.
24. Minnis AM, Padian NS. Effectiveness of female controlled barrier methods in preventing sexually transmitted infections and HIV: current evidence and future research directions. Sex Transm Infect. 2005; 81(3): 193-200.
25. Underhill K, Operario D, Montgomery P. Abstinence-only programs for HIV infection prevention in high-income countries. Cochrane Database Syst Rev. 2007; (4): CD005421.
26. Underhill K, Montgomery P, Operario D. Abstinence plus programs for HIV infection prevention in high-income countries. Cochrane Database Syst Rev. 2008; (1): CD007006.
27. Pronyk PM, Hargreaves JR, Kim JC, Morison LA, Phetla G, Watts C, et al. Effect of a structural intervention for the prevention of intimate partner violence and HIV in rural South Africa: a cluster randomised trial. Lancet. 2006, 368(9551): 1973-83.
28. World Health Organisation. Family planning: A global handbook for providers [online]. 2007 [cited 20 June 2009]. Available from URL link