Sexually transmitted genital HSV infections are estimated to affect more than 500 million people worldwide. Most of these infections are caused by HSV type 2 (HSV-2) but can also be caused by HSV type 1 (HSV-1). Genital infection with either type is lifelong and can lead to genital ulcer disease (GUD) and neonatal herpes. GUD caused by HSV-2 can recur frequently, and HSV-2 infection is also linked to increased risk of acquiring and transmitting HIV infection. In addition to potential direct effects on HSV-associated morbidity and mortality, HSV vaccines might also have indirect effects on HIV acquisition and transmission, especially in settings with a substantial burden of HIV infection. The global roadmap for advancing development of vaccines against sexually transmitted infections (ref) vaccine roadmap highlights the importance of developing a vaccine against HSV to address the substantial unmet public health need.

Although several candidate HSV vaccines have been tested in humans, currently there are no licensed vaccines against either HSV type.   IVB’s Product and Delivery Research Unit in collaboration with WHO’s Department of Sexual and Reproductive Health and Research has developed and published Preferred Product Characteristics (PPCs) for HSV vaccines to reduce the burden of HSV-associated disease, including mortality and morbidity due to neonatal herpes and other impacts on sexual and reproductive health and to reduce the acquisition of HSV-2-associated HIV infection, particularly in settings or populations with high HIV prevalence.  Two sets of PPCs are described:

• PPCs for prophylactic HSV vaccines to be used primarily before exposure to HSV-2 to prevent infection. Prevention of HSV-2 infection would prevent associated GUD and HSV transmission, including to neonates as neonatal herpes, as well as HSV-2-associated HIV acquisition.
  
• PPCs for therapeutic HSV vaccines that reduce symptomatic HSV-2 GUD in individuals who are already infected with HSV-2. For broader public-health impact, disease will need to be modified in a way that reduces HSV transmission and/or HSV-2-associated HIV acquisition.

Roadmap

Vaccines against sexually transmitted infections (STIs) are a major priority for sustainable global STI control. Development of new STI vaccines is critical because of the large number of infections worldwide, the resulting adverse sexual, reproductive and maternal-child health outcomes, and important limitations of existing STI interventions. The Global roadmap for advancing development of vaccines against sexually transmitted infections: Update and next steps reviews the progress since the first global roadmap was published ins 2014, outlines the current overarching roadmap activities, provides updates on research and development of individual vaccines against herpes simplex virus, Chlamydia trachomatis, Neisseria gonorrhoeae, and Treponema pallidum,and discusses important next steps to advance the global roadmap for STI vaccine development.