The Quest for a Herpes Vaccine

A transmitting electron micrograph of numerous herpes simplex virions. Photo courtesy of CDC/Dr. Fred Murphy; Sylvia Whitfield (1975)

Many people seem to think that the reason that scientists haven't developed a cure for genital herpes, or a vaccine, is that they aren't trying or they don't care. However, that's not true at all. Researchers have been looking for a cure for a while, as well as a vaccine. Given how much success people have had marketing fraudulent herpes treatments, a real cure would be a huge money maker. Scientists have estimated that more than 500 million people are infected with HSV-2 alone, around the globe, with another 23 million becoming infected each year.

Another huge number are genitally infected with HSV-1, which is quickly becoming the main cause of genital herpes infections in the United States.

The problem is that cure and vaccine research is very difficult to do. Some people do seem to be able to mount an effective immune response against the herpes virus, but other people can't. In addition, one of the reasons that people keep having recurrent outbreaks is that the virus hangs out and hides so effectively in the body. That makes it hard to attack.

Types of Herpes Vaccine Research

As with HIV vaccine research, herpes researchers are investigating two potential types of vaccines. The first, preventative vaccines (also known as prophylactic vaccines), are the type of vaccine most people think about when they hear the word. These vaccines would prevent people who have never been infected with herpes from contracting the infection if they were exposed.

The second type of vaccine is a therapeutic vaccine. This type of vaccine would be given to people who have herpes already in order to help them control their outbreaks - hopefully making them shorter, less intense, and less frequent. There is good reason to hope that such a vaccine could be successful, as most people do have fewer and fewer outbreaks over time.

(That is one of the reasons that fake treatments can collect such nice testimonials, many people don't need any treatment to see an improvement.) That suggests that their immune systems learn to control the infection, at least to a degree, although even people without noticeable outbreaks can still transmit the virus to others.

The State of the Science

Scientists are making progress in the search for a herpes vaccine. The developments of the chicken pox and shingles vaccines have been a big source of hope, as both conditions are caused by relatives of the genital herpes viruses. However, as there have been well over a thousand research articles published about the search for a herpes vaccine, and several trials are currently ongoing, people are honestly curious about why there isn't there one yet.

Part of the difficulty is that although animal models for herpes research do exist, the virus is well adapted to avoid the human immune system. Therefore, what works in an animal model doesn't work as well in a human.

In addition, herpes infections are much more dangerous to animals, and so testing vaccine candidates requires a delicate balance. That said, it's been difficult to achieve complete success even in an animal model. A number of different types of vaccine have been evaluated in these models and, while they've been able to reduce the frequency and severity of outbreaks, they haven't been able to eliminate infection. Even the most successful vaccines were unable to prevent the virus from colonizing the nervous system and causing asymptomatic shedding.

Another reason it's been so difficult to develop a vaccine is that human studies on herpes require thousands of participants and take years to complete. Even in high risk populations, only about 5 percent of people are newly infected with genital herpes each year! That means it takes a while to see significant results. To date, there have been few of those. Most human preventative vaccine trials have shown no or only limited success. One such limited success came from theĀ Herpevac trial for women, which suggested that the vaccine they were testing might be able to prevent genital infection with HSV-1, even though it didn't actually reduce the frequency of genital disease. However, people are hesitant to get excited too soon as at least one other trial was successful in causing an immune response but not in preventing infection.

Both the animal results and the preventative vaccine results are reasons that some researchers have chosen to primarily focus on the development of therapeutic vaccines rather than preventative ones. Results of human studies of these types of "treatment" vaccines have also been mixed, but they have been trending a bit more positive. Early trials of several vaccines have shown some success in reducing the frequency and severity of outbreaks, but the research still has a long way to go.

Looking Forward With Hope

There's a reason why I always tell people who are living with herpes that they shouldn't feel as though they've been abandoned by the scientific community. In the summer of 2014, there were at least four ongoing clinical trails testing herpes vaccines in humans, and more than 20 others had been completed. Researchers are passionate about the search for a herpes vaccine, so work continues, and I honestly believe that there is reason to hope that a successful therapeutic vaccine could be developed. Such a vaccine might not be able to prevent new infections, but it could make a world of difference to the group of individuals who currently suffer from frequent, painful recurrences and even more painful stigma.

Awasthi S, Friedman HM. (2014)Status of prophylactic and therapeutic genital herpes vaccines. Curr Opin Virol. 6C:6-12. Accessed on 6/7/2014

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