Herpes, whether oral or genital, is both common and incurable. While HSV-1 usually causes oral herpes and HSV-2 usually causes genital herpes, either virus can infect both mouth and genitals. And, while over half of Americans have oral herpes and one in six has genital herpes, it's still among the more stigmatized STIs. As we fight the shame and misinformation that surround the infection, scientists are working to prevent it entirely — and they've just made a groundbreaking discovery. Researchers from the Albert Einstein College of Medicine of Yeshiva University have developed a vaccine that prevents both active and latent HSV-2 infections — the first-ever vaccine to do so. Traditionally, scientists have assumed that an HSV-2 vaccine would have to expose the immune system to small amounts of gD-2 (the viral protein that allows HSV-2 to enter human cells) to prompt the immune system to create antibodies, which fight gD-2 and keep HSV-2 out of the cells. The Einstein College team circumvented that approach, instead deleting the gD-2 gene from the HSV-2 virus and then exposing rats to the gD-2-free virus. The rats' immune systems obviously didn't produce antibodies to fight the missing protein — but, they did produce antibodies connected with a different immune system response that actually succeeded in warding off herpes infection. Study co-leader William Jacobs Jr., PhD, compared gD-2 to "a Trojan horse that misleads the immune system" — and has distracted researchers for years. The Einstein team isn't sure exactly why the protein-deleting tactic works so well, but they're heartened that it does and hopeful that it could work to prevent oral herpes, too. And, this development isn't only promising where herpes is concerned: The microbes that lead to HIV infections and tuberculosis enter cells in much the same way as HSV-1 and HSV-2 do, meaning that this discovery may shed light on how to fight those diseases, too.