Only about 3% of women are infected in their lifetime by these four types of HPV (Types 6, 11, 16, 18) targeted by the vaccine.<ref>This was confirmed by a study published February 28, 2007 in the Journal of the American Medical Association, JAMA 297(8):813-819, February 28, 2007.</ref> | Only about 3% of women are infected in their lifetime by these four types of HPV (Types 6, 11, 16, 18) targeted by the vaccine.<ref>This was confirmed by a study published February 28, 2007 in the Journal of the American Medical Association, JAMA 297(8):813-819, February 28, 2007.</ref> |