Consistent and correct condom use reduces risk of bacterial STIs by 60%

Consistent and correct condom use provides a high level of protection against bacterial sexually transmitted infections (STIs), US investigators report in Sexually Transmitted Infections. Individuals who always used condoms correctly were almost 60% less likely to be diagnosed with an infection. Consistent condom use on its own did not reduce the risk of bacterial STIs.

“Efforts to promote condom use should be augmented with efforts to promote their correct use,” write the authors. “Condom use errors and problems are a global issue. Incomplete use of condoms is a problem requiring targeted education. Rectifying issues such as poor fit and feel of condoms and using oil-based lubricants may substantially reduce slippage and breakage.”

Condoms are a cornerstone of HIV prevention and sexual health campaigns.

A number of well-designed studies have shown their protective effect against male-to-female transmission of herpes, chlamydia, gonorrhoea, syphilis and human papillomavirus (HPV).

However, whether condoms provide protection against the acquisition of STIs remains controversial.

Research looking at this question has had number of important limitations. The most important of these is a failure to adjust for incorrect use of condoms (not using condoms from the start to the finish of penetrative sex) or condom 'accidents' such as slippage and breakage.

“Failure to control for condom breakage and slippage may produce the analytical equivalent of condom non-use,” observe the investigators. “A prospective study of clinic attendees found 13% incidence of chlamydia and gonorrhoea among people reporting consistent condom use but also reporting at least one problem with incorrect use. In contrast, among those reporting consistency and lack of problems…no incident infections were found.”

Previous research has also relied on study participants accurately remembering whether they used condoms and if they encountered problems.

Investigators in the US therefore designed a prospective study involving attendees at five sexual health clinics. Participants received daily prompts to electronically recall incidents of penile-vaginal sex and use of condoms.

The investigators wanted to see if consistent condom use was protective against three common bacterial STIs: chlamydia, gonorrhoea and trichomonas. They also wished to determine the protective effect associated with consistent and correct use of condoms.

A total of 929 people were recruited to the study. A urine sample was taken at the start of the study to screen for STIs and further samples were submitted for testing after three and six months of follow-up.

Most of the study participants were women (55%) and African American (65%). Their mean age was 29 years and the mean number of reported lifetime sexual partners was 30.

Participants reported a total of 14,970 penile-vaginal sex events, 64% of which involved the use of a condom. Approximately a quarter of sex events (24%) with a condom involved an error or problem.   

A total of 118 STIs were diagnosed during follow-up.

Incidence of STIs was 8.46% among those reporting less than consistent condom use. This compared to an incidence of 6.71% in people who reported using condoms all the time. This difference was not statistically significant.

The incidence of infections among people who reported less than consistent use of condoms and incorrect use of condoms or problems with slippage or breakage was 8.75%. The incidence among individuals who reported consistent and correct condom use was significantly lower at 3.35% (p = 0.023).

“Participants who used condoms both correctly and consistently were estimated to have 59% smaller odds of acquiring an STI over 3 months compared to participants who did not use condoms both correctly and consistently,” note the authors. “Magnified over an entire population, this level of risk reduction for sexually active people is substantial.”

They believe that their findings probably underestimate the protective effect of condom use against bacterial STIs: “The six incident cases observed for people using condoms consistently and correctly may be a result of an unprotected sex event, breakage event, etc that was not reported….tendencies to forget, fabricate, exaggerate and under-report are inevitable.”

Crosby RA et al. Condom effectiveness against non-viral sexually transmitted infections: a prospective study using electronic daily diaries. Sex Transm Infect, online edition. DOI: 10. 1136/sextrans-2012-050618, 2012.