The herpes simplex virus 2 (HSV 2) is spread via genital contact and oral sex. Once infected, patients remain carriers for life. A large number of people who have HSV will never experience any symptoms, while others may suffer frequent outbreaks and painful genital sores. Prevention of HSV 2 outbreaks is particularly critical for pregnant women because the virus can cause neurological damage in newborns.
According to the World Health Organisation, 417 million people worldwide have HSV 2. So why has no one developed a vaccine yet?
Given its prevalence and high risk of infection, many research teams have tried to develop a vaccine for genital herpes. There is little argument that effective vaccination would reduce the frequency of transmissions and help contain the spread of HSV 2.
Early vaccination trials date back more than 80 years and some clinical trials have been successful in reducing the severity of HSV 2.
One of the largest, the Herpevac Trial, involving 8,300 women, showed promise in preventing HSV type 1 but not HSV 2. Because of the high rate of failure, many pharmaceutical companies have abandoned their research into developing a vaccine for HSV 2.
Among the reasons why it’s been so difficult to develop effective vaccination is that the herpes virus is “smart”. It’s had around six million years to evolve and adapt to humans. Researchers have also noted that the two types of the virus (HSV 1 and HSV 2) can trade genes and continue to evlove, which makes vacccine development even harder.
Genital herpes outbreaks are caused by HSV 2 infection, but there are studies that have documented HSV 1 as being the cause of genital herpes. For example, one study found that 37% of women with genital herpes carried HSV 1.
Genital herpes is spread via vaginal, anal or oral sex. Carriers are more contagious during times when they have an active outbreak of herpes.
At present, there is no cure for HSV 1 or HSV 2. Once a person becomes infected, they are carriers for life. Many patients may never know that they are carriers and experience no outbreaks. Symptoms of a genital herpes outbreak may include:
Initially, a herpes outbreak may be quite severe. Subsequent outbreaks are often less intense and tend to heal faster.
Living with genital herpes is completely manageable. Treatments for genital herpes include antiviral medications such as famciclovir and valacyclovir, which prevent outbreaks and reduce the severity of symptoms. There are also several self-care options to minimize discomfort including painkillers, creams, and strategies to reduce itching such as hot or cold compresses.
Scientists continue to explore options for a herpes vaccine. In September 2019, a team at the University of Pennsylvania successfully tested a vaccine for genital herpes in mice.
Of the 64 infected mice, 63 mice were immune to HSV 2, 28 days after vaccination.
“We’re extremely encouraged by the substantial immunizing effect our vaccine had in these animal models,” explained Harvey Friedman, professor of infectious diseases at the University of Pennsylvania. “Based on these results, it is our hope that this vaccine could be translated into human studies to test both the safety and efficacy of our approach.”
Because HSV 2 infections in mice are quite different from those in humans, the group then exposed 10 guinea pigs to the virus, as their response to the virus is more similar to humans. After vaccination, none of the animals developed genital herpes.
In July 2019, US biopharmaceutical company BlueWillow Biologics announced that it had applied for a patented nasal vaccine for herpes. According to clinical trials using guinea pigs, the intranasal spray reduced the severity and spread of genital herpes by over 50%.
"Genital herpes is easily and often unknowingly transmitted between partners. The lifelong infection frequently causes psychological distress and negatively impacts quality of life," said Dr. Ali Fattom, Senior Vice President of Vaccine Research and Development at BlueWillow. "After years of research in animals, we are moving closer to studies in humans where we expect results to validate the potential of this much-needed vaccine."
Although research into a genital herpes vaccine still has a way to go, it seems that we are edging closer to a solution.