Second-generation prophylactic HPV vaccines: current options and future strategies for vaccines development

Two vaccines focused on the prevention of HPV-related diseases have been introduced in the last decade, the quadrivalent vaccine Gardasil and the bivalent vaccine Cervarix. They are targeted to prevent precancerous and cancerous lesions not only of the cervix, but also of the vulva, vagina, anal and head-neck region. Furthermore, the protection of the quadrivalent vaccine Gardasil includes also genital warts and recurrent respiratory Papillomatosis, two benign conditions with high socio-economic impact. Although their efficacy in reducing the burden of HPV-related pathologies has been already documented, second-generation HPV vaccines are being developed in order to overcome major limitations, above all the cost of production, distribution and acceptance, thus promoting an easier access to vaccination, especially in developing countries. Recently a new multivalent VLP vaccine active against nine HPV subtypes, called Gardasil 9 (Merck & Co., Inc., Whitehouse Station, NJ, USA), has been approved, showing promising preliminary results. In this article, we outline the strategies adopted for second-generation HPV vaccine engineering, the latest HPV vaccines available at this time, as well as those currently in development.