Human Papillomavirus Vaccine

Human papillomavirus (HPV) is a double-stranded DNA virus. HPV infects skin and mucosal cells and tissues. So far, more than 200 different types of HPV have been identified based on differences in DNA genomic sequences, also called genotypes. Sixteen HPV genotypes are classified into the high-risk category, including types 16, 18, 31, 33, 34, 35, 39, 45, 51, 52, 56, 58, 59, 66, 68, and 70.³ Among these, types 16 and 18 are known to cause 70% of cervical cancer. Additional cancer types associated with HPV infection and the percentage of each cancer type caused by HPV are summarized in Table 1.

HPV vaccines are designed as a prophylactic measure against HPV infection. High-risk genotypes described above are the primary targets. Available HPV vaccines approved by the U.S. Food and Drug Administration (FDA) include Gardasil and Cervarix.

Gardasil^®, the first-generation human papillomavirus (HPV) vaccine manufactured by Merck, received FDA approval in 2006. Gardasil^® targets four types of HPV, namely 6, 11, 16, and 18, hence a 4-valet vaccine or 4vHPV. The second-generation HPV vaccine called Gardasil^®9 was approved by the FDA in 2014. With a much wider range of protective coverage, Gardasil^®9 targets HPV 6, 11, 16, 18, 31, 33, 45, 52, and 58, hence a 9vHPV.⁴ There is a third type of HPV vaccine called Cervarix that targets only HPV 16 and 18, hence a 2vHPV vaccine. In the US, only Gardasil^®9 has been distributed since 2016. Gardasil and Cervarix continue to be in use in other parts of the world.