The Impact of Cumulative Effectiveness

Cumulative effectiveness refers to the likelihood of becoming infected with an STD over time. In other words, to what extent does sexual activity with an infected partner over an extended period of time increase the risk – that is, create a cumulative risk? And to what extent are condoms effective at reducing this cumulative risk – that is, provide cumulative effectiveness?

Authors Mann, Stine and Vessey published an article in June of 2002 that expanded on this concept of cumulative effectiveness. These researchers used the role of disease-specific infectivity and the number of disease exposures to determine the long-term effectiveness of the latex condom.¹ The authors explored the scenario of females having sex with males infected with gonorrhea. The risk of females acquiring gonorrhea from infected males is believed to be 50 percent from one act of sex without using a condom.²

For their calculations the authors used a 3 percent slippage and breakage rate. Assuming the condoms were used correctly and allowing only for a 3 percent chance of slippage and breakage, 1.5 percent of women in this scenario would be expected to acquire gonorrhea after one act of sex with an infected partner. After 10 acts of sex one would expect 14 percent of the women to become infected and after 30 acts of sex with an infected partner, the expected risk would escalate to 37 percent even with perfect condom use. While the authors did not address the scenario of incorrect or inconsistent use, one would expect these additional factors to dramatically increase one’s risk of infection. 

1 Mann JR, Stine CC, Vessey J. The role of disease-specific infectivity and number of disease exposures on the long-term effectiveness of the latex condom. Sex Transm Dis. 2002;29:344-349.

2 Hooper RR, Reynolds GH, Jones OG, et al. Cohort study of venereal disease. I: The risk of gonorrhea transmission from infected women to men. Am J Epidemiol. 1978;108:136-144.

Medical Institute, http://www.medinstitute.org/CumEff.htm