Kerry Girard isn’t ready to talk about sexually transmitted diseases with her 11-year-old daughter. But that doesn’t mean the Rockland mom isn’t looking to protect her from them. That’s why Girard decided to have her daughter receive Gardasil, a vaccine approved for young girls that protects against one of cervical cancer’s most common causes: a sexually-transmitted infection known as HPV, or human papillomavirus. Federal health officials began to recommend more girls receive the vaccine earlier this year. A study released this month underscores one reason why. Teen sex rates nationwide have dropped only marginally from 1991 to 2007, while a recent increase in condom use has appeared to stagnate, according to the federal Centers for Disease Control. But some parents, even medical professionals, are reluctant to get the vaccine for their young teen — or tween — daughters. “I personally would find that an awkward conversation with my 10-year-old,” said Sue Joss, executive director of the Brockton Neighborhood Health Center. Evelyn Reilly, public policy director for the conservative think-tank the Massachusetts Family Institute, sees no reason for vaccinating young girls against an STD. “If you don’t sleep around, you’re not going to get it,” she said. Their comments underscore the range of attitudes parents of daughters have toward the vaccine. Gardasil was approved in 2006 for girls and women from 9 to 26 years old. It is completed ...