CHICAGO (CBS) — On this World AIDS Day, we have some good news to report: A historic decline in the disease.

However, concern in Chicago remains over a drug that can prevent HIV. The brand name is “Truvada,” but you may have seen ads for the generic name, “PrEP.”

CBS 2’s Dorothy Tucker explains the fears over a possible mixed message.

On the corner of Madison and Pulaski, World AIDS Day is marked by free HIV testing, which includes a complimentary dinner, as well as immediate results.

In a Friday press conference, the Chicago Department of Public Health said new cases of HIV are down 55 percent since 2001. One reason for the decline, here and worldwide, is the introduction of PrEP.

“We now have a pill that can be taken once a day that’s up to 99 percent effective of preventing HIV when taken consistently,” said John Peller, AIDs Foundation of Chicago CEO.

Peller says while PrEP is a popular drug among white gay men, it’s important to inform other communities about the pill, as well.

Harold Cherry, however, a community health activist, is concerned PrEP sends a dangerous message to some.

“If you tell me PrEP is going to stop me from being infected, then I’ll think that that’s the cure-all, so now I don’t need to use condoms or do nothing else — I just need to take PrEP,” Cherry said.

PrEP does not prevent STD’s or pregnancy, Peller adding that people are advised to always use condoms.

“Frankly, people just aren’t using them, so it’s critical to have a range of options for people who want to have sex the way they want to have sex,” Peller said.

Most insurance companies cover the cost of PrEP. It’s also available for free through government funded programs.