However, a new HSV-2 vaccine is now in the early stages of human clinical trials, and researchers are once again hopeful they may have a winner.
The problem is that the herpes virus has biological defences that make it hard to destroy. The herpes virus has the ability to go dormant – which happens when it is attacked by antibodies – and while dormant it is effectively in stealth mode, and doesn't produce the proteins that signal its presence. Not only that, but it hides out in your nervous system – where antibodies can't get at the virus. To add to this, HSV-2 interferes with the activity of antibodies, T cells, and other major components of the immune system.
However, the success of vaccines for chickenpox and shingles, which are caused by a related herpes virus known as varicella-zoster virus, suggests that a vaccine for HSV-2 should be possible.
The problem of HSV-2
According to the Centers for Disease Control and Prevention (CDC), at least 45 million people ages 12 and older in the United States, or one in six adolescents and adults, have genital herpes. They estimate that annually, 776,000 people in the United States get new herpes infections.
Most people with the disease are unaware that they have it. Some develop painful symptoms, such as recurring sores around the genitals or rectum. The virus is transmitted almost exclusively through sexual contact, though pregnant women with herpes outbreaks can also infect their babies during delivery.
Herpes is unpleasant enough by itself – but even worse, public health officials have discovered that those infected with HSV-2 are more likely to become infected with HIV too – and become carriers of both diseases.
Failure of previous HSV-2 vaccine
It can be difficult to develop a vaccine that is effective, but safe.
The vaccine against chickenpox uses a live, weakened version of the virus which is injected into a person’s body to stimulate an immune response, but this may not be the most appropriate way to develop an effective HSV-2 vaccine.
One vaccine was promising enough to proceed to full clinical tests. But in a randomized, double-blind clinical trial involving 8,323 women, the vaccine did not prevent infection by HSV-2 — although it did offer some protection against a closely related virus, HSV-1. (See this article published in Nature in January 2012 for full details.)
Clinical trial of new investigational HSV-2 vaccine being launched by NIH
The National Institute of Health (NIH) is about to begin an investigative clinical trial of a newly developed HSV-2 vaccine. This early trial is only to investigate the vaccine's safety, and so it is being tested at this stage only on those already infected by herpes simplex 1 or herpes simplex 2.
"Although genital herpes is treatable, it is a lifelong infection that can exact a substantial psychological and physical toll on infected individuals and places them at higher risk of acquiring HIV,” said NIAID Director Anthony S. Fauci, M.D. “Furthermore, mothers with active genital herpes infection at time of delivery can transmit the virus to their newborns, which can lead to severe illness and death.
“A protective vaccine would help to reduce significantly the spread of this all-too- common sexually transmitted infection,” Fauci added.
This newest HSV-2 vaccine has been developed from the collaboration of two research laboratories led by Dr David Knipe, Ph.D., professor of microbiology and immunobiology at Harvard Medical School, Boston, and Dr Jeffrey Cohen, M.D., chief of NIAID’s Laboratory of Infectious Diseases.
The study is expected to be completed by October 2016.
An effective HSV-2 vaccine would be great news from a public health point of view, and for those who are most at risk of getting infected (those who are most sexually active, with multiple partners).
But it does nothing to help those who have already been infected… or for those who might be monogamous, but with a partner who isn't.
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