I suspect that a mandate requiring Gardasil except when opting out made it covered by insurance for all who took it...
Correct. In 2005, the Texas legislature directed a study be done on how to reduce and eliminate cervical cancer and report to the governor. The report came in 2006 and said vaccination met the goal. Perry signed the order in 2007 not only having opt-out per Texas law but making it easier than every to opt-out. The reason it was opt-out, not opt-in, was to ensure coverage by Medicaid and health insurance providers.