Background:
Screening sexually-active women aged ≤25 years for chlamydia is recommended. To supplement screening/treatment programs for young women some areas target high-risk males.

Objective:
To determine if screening men aged 20-24 years in prison would affect FPC chlamydia positivity rates in females aged 20-24 years from the prisoners' home ZIP Code.

Method:
Using census and screening data, we identified ZIP codes of residence for men aged 20-24 tested and treated for chlamydia in prison, and formed groups based on the most (“High-positivity”) and least (“Low-positivity”) percentage of men. We compared changes in chlamydia test positivity for women aged 20-24 years from these ZIP codes attending FPCs. We measured positivity changes for females in FPCs before (1999-2001) and after (2001-2004) the prison screening program began.

Result:
In 18 high-positivity ZIP codes, 1054 (4.54%) of 23,203 men were treated for Chlamydia in prison in 2002-2004. Among women from those areas attending FPCs, test positivity fell from 10.58% in 1999 to 8.65% in 2001, and 7.39% in 2004; a fall of 18.2% before and 14.6% after the prison screening program began. In 18 low-positivity ZIP codes, 98 (0.47%) of 21,057 men were treated in prison in 2002-2004. Among women from those areas attending FPCs, test positivity fell from 7.31% in 1999 to 5.37% in 2001, and 4.16% in 2004; a fall of 26.5% before and 22.5% after the prison screening program began.

Conclusion:
Despite a large number of males infected with Chlamydia being identified and treated, we were unable to attribute the continued decline in female positivity in FPCs directly to screening and treating males in prison for this age group.

Implications:
Further research into the association between screening males for chlamydia and female positivity rates should be done to better understand this relationship.