According to information the manufacturer of Gardasil, a vaccine against human papillomavirus, presented to the FDA prior to approval, if a person has already been exposed to HPV 16 or 18 prior to injection, then Gardasil increases the risk of precancerous lesions, or worse, by 44.6 percent.
This information is not advertised, and the FDA has not recommended screening for HPV prior to vaccination. The FDA did not even demand that a warning be included in the package insert.
According to Examiner.com:
"Now, Merck's research is indicating that Gardasil may also 'provide cross-protection' against other strains of HPV that are closely related to HPV 16 and 18 ... This means prior exposure to these additional strains may pose an increased risk for cervical cancer also, if combined with vaccination."