Which HPV strains are most commonly responsible for oropharyngeal cancers?

HPV 16 is the most oncogenic HPV strain and is responsible for approximately 85–90% of HPV-positive oropharyngeal cancers. HPV 18 is the second most common high-risk strain, more commonly associated with cervical adenocarcinoma. Both HPV 16 and 18 are high-risk oncogenic strains that encode E6 and E7 oncoproteins, which inactivate p53 (tumor suppressor) and Rb (retinoblastoma protein), respectively, leading to uncontrolled cell proliferation. HPV 6 and 11 are low-risk strains associated with genital warts and recurrent respiratory papillomatosis (not cancer). The Gardasil 9 vaccine covers HPV 16 and 18 among other high-risk strains.