Progress in Developing a Herpes Vaccine

Herpes virus, artwork
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The search for a vaccine to protect against oral herpes and genital herpes has been a long one. Researchers have been experimenting with possible vaccines since at least the early 1930s. Unfortunately, there has been little success. While herpes vaccines have been developed for mice, human trials have largely been unsuccessful. Although some herpes vaccines have initially appeared to have promise, more stringent testing has shown them to be no better than placebo.

Existing Herpes Virus Vaccines

Technically speaking, there are already several herpes vaccines on the market. However, while these vaccines protect against viruses in the herpes family, they don't protect against genital or oral herpes.

The shingles vaccine and the chickenpox vaccine are examples of two ways that a herpes simplex vaccine could work. The chickenpox vaccine, or varicella-zoster virus (VZV) vaccine, is given to protect against individuals ever becoming infected with VZV. In contrast, the shingles vaccine is given to reduce the likelihood that an existing virus will reactivate, causing symptomatic shingles.

These are similar to the two types of vaccines that have been proposed to protect against oral and genital herpes. One type of vaccine would be for people who have never been infected, to protect against the virus. The other type of vaccine would be for people who already have herpes, to protect against outbreaks.

Herpes Vaccine Priorities From the World Health Organization

Theoretically, it makes sense that a vaccine could work to prevent herpes outbreaks. After all, in many people, the immune system controls herpes infections so that they never have symptoms. This makes the virus a good target for a therapeutic vaccine, although not as good a target as HPV. Unfortunately, the herpes simplex viruses that cause genital and oral herpes have proven to be difficult to control with vaccines.

In 2017, the World Health Organization (WHO) defined a series of priorities for developing a herpes vaccine. These priorities were the result of a conference of stakeholders who came from around the world to determine what characteristics of a herpes vaccine would be most important. The group of priorities that they came up with were:

  • To reduce the number of people who become infected with HIV because they have a herpes genital infection. (Genital sores increase the risk of HIV transmission). 
  • To reduce the number of people negatively affected by HSV. This includes reducing both the physical and psychological symptoms of herpes. It also includes reducing the risk of serious consequences of herpes, such as neonatal herpes.
  • To reduce the impact of herpes infection on reproductive health.

WHO suggested that two types of vaccines could be useful for herpes simplex infections. Prophylactic vaccines, like the chickenpox vaccine, would help prevent people from ever getting herpes. Therapeutic vaccines, like the shingles vaccine, would reduce the number of outbreaks.

Herpes Vaccine Research

There have been some promising trials of herpes vaccines. However, to date, no human trials have shown high enough efficacy to bring a herpes vaccine to market. That said, there is hope for vaccine development. Scientists have managed to protect some subgroups of people against herpes infection.

Unfortunately, there are several hurdles scientists have to face when developing a herpes vaccine. The biggest hurdle is that there is no good animal model in which to test the vaccines. Although mice and guinea pigs can be infected with herpes, their infections are quite different from human herpes infections. This means that vaccines that have shown promise in animals have not been particularly successful in humans.

Herpes vaccines are also difficult to study for several other practical reasons. You need to test a lot of people to see if they work. Those people can be hard to find. In addition, since many people don't have herpes symptoms, you can't just wait to see if people have an outbreak. You have to test to see whether they've been infected with the virus. Or, for therapeutic vaccines, you have to test how the vaccine has affected the amount of virus they shed. Addressing any of these factors can make vaccine trials both slow and expensive.

The Future of Herpes Vaccine Research

Around the world, doctors and scientists are aware that stopping herpes is a priority. Although many people who are infected with the virus have no symptoms, herpes can have a significant impact on people's lives. This is particularly true for people who become infected during pregnancy or who live in areas with a lot of HIV.

That's why herpes vaccine research is so important. People are continuing to look for novel ways to prevent herpes infections and reduce outbreaks. One research group, for example, is using lasers as part of their vaccination procedure. Their goal is to stimulate immune cell development in the layers of the skin. But there are no quick answers. Fortunately, there are other options for reducing the risk of herpes transmission. Both suppressive therapy and reliably practicing safe sex can help protect individuals when their sexual partners are infected with HSV.

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