Human papillomavirus vaccine: Success and challenges

Persistent infection with high-risk human papillomavirus (HPV) is a major etiological cause of cancers associated with the cervix, anogenital region, vulva, vagina, penis, and oropharynx. Cervarix®, Gardasil®, and Gardsil9® are three approved prophylactic vaccines that can effectively provide protection against HPV infection. However,they only offer protection against a limited number of HPV strains, not all of which can cause cervical cancer (CC). Additionally, they only provide limited therapeutic advantages against HPV infections that have already been established. Thus, developing a therapeutic vaccine is urgently required and is the need of the hour. Unlike normal cells, two of the viral early proteins, E6 and E7, are persistently expressed in tumor cells. This makes these two proteins the prime candidates for therapeutic vaccines that aim to eliminate the infected cells by cytotoxic T-lymphocytes without affecting normal cells. Therapeutic vaccinations are being researched and are under trials, and no such vaccines have yet been authorized. The development of a therapeutic vaccination coupled with currently available prophylactic vaccines is anticipated to significantly lower morbidity and cancer load globally. This review aims to provide a clear understanding of the molecular basis, immunogenicity, effectiveness, and challenges of current prophylactic vaccines and the future scope of implementing therapeutic vaccines against infection caused by HPV.