Vaccines

Both preventive and therapeutic genital herpes simplex virus (HSV) vaccines are being explored, and scientists generally agree that development of these vaccines should be feasible. Previous preventive vaccine candidates did not demonstrate high efficacy in Phase 3 trials. However, new products are under development.

Several therapeutic vaccine candidates have entered clinical trials in recent years, including one led by Sanofi Pasteur, Immune Trial Design, PATH and NIAID that is expected to report results in mid-2024.

Modeling studies also demonstrate that both types of vaccines could have significant public health and economic impact, including reduction of HIV infections and savings of hundreds of millions of dollars in healthcare costs.

WHO has published preferred product characteristics to help ensure potential preventive and/or therapeutic genital herpes vaccines will best meet public health needs, especially in low- and middle-income countries. This document notes that while therapeutic vaccines may be easier to develop and would have some important benefits, a preventive vaccine would be ideal, because:

• Only a relatively small proportion of people with genital herpes have symptoms and seek care
• Even if their symptoms are suppressed, people with genital herpes infection remain at increased risk for HIV acquisition
• A preventive vaccine would be more straightforward to administer within existing immunization infrastructure, for example by delivery to all adolescent girls and boys

The WHO document also identifies preferred characteristics for each type of vaccine, including vaccine indications, target populations, type of vaccine administration, delivery strategies efficacy requirements, duration of protection, schedule, and safety requirements.

Testing

Virologic testing of samples from active genital herpes lesions offer the best way to diagnose the infection. Viral cell culture has historically been the gold standard for detecting infections, but molecular testing has shown to be more sensitive in recent years. Additional tools are needed to better diagnose HSV and control the spread of these infections.

Source: WHO Preferred Product Characteristics