CHICAGO (CBS) — Public health officials in Chicago have teamed up with high school and college students to launch an ad campaign to encourage people to practice safe sex; and, to that end, they passed out free condoms on Tuesday.

As part of World AIDS Day on Tuesday, the Chicago Department of Public Health, a group of students, and a non-profit ad agency kicked off a new public education campaign called “Chicago Wears Condoms.”

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The campaign includes billboards and bus ads featuring the Chicago skyline draped on condoms in the colors of the Chicago flag.

CTA passengers did double takes at the Roosevelt station in the South Loop as one student from the Illinois Institute of Art wore a flapper-style dress made of condoms as she helped hand out free condoms Tuesday morning.

“Everybody wants to stop and say, ‘Oh my gosh, are those condoms?’ because, in fact, they are condoms,” said Mallory Pfeiffer.

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The students said they wanted to encourage open discussion about safe sex.

“Too often, we see adults with good intentions trying to create ads to impact teens, but not too often are they really effective,” said Daniel Heather, a high school student with the Mikva Challenge.

The students came up with the visual of Chicago buildings clad in condoms.

“I think it’s just a great reminder to everyone about the importance of preventing serious infections, like HIV, chlamydia, gonorrhea, and syphilis,” said Chicago Public Health Commissioner Dr. Julie Morita.

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She said the campaign is meant to remind people condoms prevent both sexually transmitted diseases and unplanned pregnancy. For more information about the campaign, call 800-243-2437.