HPV Vaccines - An Overview

Human papilloma viruses (HPVs) are a group of viruses that can infect the stratified epithelium of the skin and mucosa. Based on their oncogenic potential, they can be divided into high risk and low risk types. HPV accounts for 7,30,000 cases of cancers all over the world. In June 2006, the first HPV vaccine - Gardasil - was approved by the FDA. After this in 2007, Cervarix was approved and finally Gardasil 9 in 2014. Currently, there are six prophylactic vaccines against HPV, of which five have been pre-qualified by WHO. The bivalent vaccines offer protection against acquiring HPV 16 and 18, which cause 70% of cervical cancers. The quadrivalent and nonavalent vaccines offer additional protection against low-risk HPV 6 and 11. The currently available vaccines have been found to be safe in both pre- and post-licensure trials. The vaccines offer excellent protection against cervical intra-epithelial neoplasia of grade 2 and 3. The role of HPV vaccines in prevention of other cancers is mostly supported by small retrospective studies. The currently available vaccines are approved for prophylactic use only. There have been attempts to use HPV vaccines therapeutically, and there are conflicting reports regarding their efficacy. This article reviews the currently available vaccines, their indications, adverse effects, contraindications, and epidemiological impact. It also highlights the off label therapeutic uses in various conditions and other potential vaccine candidates.