Effectiveness of Condoms in Preventing Sexually Transmitted Infections

Date of publication: June 2005

The Ministry has consistently provided information with the following themes:

• Individuals should decide when they are ready to have sex and should not feel pressured to have sex when they are not ready

• There is no such thing as ‘safe sex - only ‘safer’ sex

• Using condoms consistently significantly reduces the risk of catching a sexually transmitted infection

• Don’t have sex with someone who has an STI

• Many teenagers will have sex. Using a condom significantly reduces the likelihood that they will catch and transmit a sexually transmitted infection.

What scientific evidence is there showing the effectiveness of condoms in preventing sexually transmitted infections and how is this interpreted?

A key question sometimes asked is what scientific evidence is there showing the effectiveness of condoms in preventing sexually transmitted infections and how is this interpreted?

The Cochrane Collaboration, an internationally recognised organisation that promotes systematic reviews of the benefits and risks of health treatments, has published a meta analysis (a systematic review of the combined collective results of previous research)of condom effectiveness in reducing HIV infection.

The study concluded:

'This review indicates that consistent use of condoms results in 80% reduction in HIV incidence. Consistent use is defined as using a condom for all acts of penetrative vaginal intercourse. Because the studies used in this review did not report on the "correctness" of use, namely whether condoms were used correctly and perfectly for each and every act of intercourse, effectiveness and not efficacy is estimated. Also, this estimate refers in general to the male condom and not specifically to the latex condom, since studies also tended not to specify the type of condom that was used. Thus, condom effectiveness is similar to, although lower than, that for contraception.'

A similar meta analysis of studies of condom effectiveness in preventing sexually transmitted infection is currently underway (refer to the Cochrane Database). The great majority of practitioners in sexual health believe that in the absence of this further analysis it makes good sense to infer from the HIV study that a similar level of protection is offered against other infections where the infectious agent is spread in the same manner (eg gonorrhea, syphilis and chlamydia).

In fact there are a number of relatively recent studies using randomized controlled trials - regarded as the gold standard for scientific studies - that point to the effectiveness of condoms in lowering STI rates. The studies below are all listed on the Cochrane Central Register of Controlled Trials:

• a Uganda study of consistent condom use significantly reduced incidence of syphilis, gonorrhea and chlamydia - AIDS (London, England) 15 (16): 2171-9, 2001 Nov

• a Singapore study of gonorrhea rates in Singapore sex workers showed low rates (0.4 episodes per worker per year) where condom use was high (75%) - Intl Jnl of STD and AIDS. 5(4):268-72, 1994

• an Indian study showing alarmingly high rates of HIV and STDs in female sex workers concluded that even a partial increase in condom use may reduce the transmission of HIV and STDs - AIDS (London, England) Vol 9 Suppl 1, pp S21-30, 1995 Jul

• a US study concluded promising effects were also observed for chlamydia infections with encouraging condom use with African American adolescent girls -JAMA 292(2):171-9,2004 Jul.

It's important to be aware of the limitations of science in studying an area which is inherently difficult. Hundreds of other studies have been done, some with limited methodology.

For example, in the Bulletin of the World Health Organisation, the authors say:

'The panel strongly cautioned the public against misinterpreting the scanty evidence. The small number of well designed prospective studies precluded the panel from making judgments about the effectiveness of condoms in preventing other STIs; the reviews stated that the lack of data were not to be construed as evidence either supporting or denying the effectiveness of condoms.' From - King K, Levine R, Weaver M. 2004. Effectiveness of condoms in preventing sexually transmitted infections. Public Health Reviews: Bulletin of the WHO.

There are significant difficulties in accurately interpreting these scientific studies because

• a number have methodological problems
• their findings are often contradictory
• individual studies have different strengths and weaknesses
• individual studies frequently only shed light on one question at a time and often in only a very limited manner.

The Bulletin of the WHO, referred to above, outlines the difficulties in conducting meaningful studies in this area but concludes:

'In view of these issues, it seems remarkable that data from longitudinal studies and the one randomized trial as well as several cross-sectional or case–control studies have nonetheless demonstrated the statistically significant effectiveness of condoms in protecting against HIV and most of the other STIs examined.'

The approach the Ministry takes is to base its strategies on the best evidence available, through the use of systemic reviews and meta analyses (where studies are screened, weighted, pooled and collectively analysed).

The Bulletin of the WHO, referred to above, concluded its review:

'Since 2000 important new evidence ...has come to light to support the effectiveness of condoms in preventing STIs in men and women. In no study has the effectiveness been 100%. Nonetheless, even partially effective interventions can have a major impact on controlling the spread of STIs in the population (36). ...Condom promotion represents an important component of comprehensive HIV-prevention and STI-prevention strategies.'

The Ministry also uses appropriate review and guidance by appropriate experts, community and sector leaders. For instance in developing our sexual and reproductive health strategy, from which the Hubba campaign developed, the Ministry formed a Sector Reference Group consisting of:

Nigel Dickson, Department of Preventive Medicine, Otago University
Pania Ellison, Te Puawai Tapu
Kitty Flannery, President, New Zealand Venereological Society
Alan Flemming, Principal, St Bernard’s School
Rick Franklin, Association of Sexual Health Services, Clinical Director of Auckland Sexual Health Service
Gill Greer, CEO, New Zealand Family Planning Association
Kevin Hague, Director of the New Zealand AIDS Foundation
Ingi Hayward, Northland Health Peer Sexuality Education Programme
Catherine Healy, New Zealand Prostitutes Collective
Pippa Mackay, recent Chairperson New Zealand Medical Association
Fuimaono Karl Pulotu-Endemann, Pacific Consultant
Gillian Tasker, Christchurch College of Education
Olivia Tusa, Hutt Valley Health

When providing information to the public, the Ministry provides appropriately targeted and summarised information for public health campaigns, backed up by more detailed information from a number of sources to provide further detail if people seek that.

A systematic review of the effectiveness of primary health programmes to prevent STDs in adolescents concluded that interventions should focus on the provision of condoms, information and demonstration of their use - J.Adolesc Health 1996;18:387-96.

For more information

For more information on this issue contact:

Dr Sue Bagshaw,
Christchurch,
198 Youth Health Centre

Dr Christine Roke,
Family Planning Association

Dr Jane MacDonald,
Wellington Sexual Health Service

Dr Nicky Perkins
Auckland sexual health

Dr Edward Coughlan
Christchurch sexual health

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Related information

Sexual Health in New Zealand