As with almost all sexually transmitted infections, women are more susceptible to acquiring genital HSV-2 than men.[41] On an annual basis, without the use of antivirals or condoms, the transmission risk of HSV-2 from infected male to female is about 8–11%.[37][42] This is believed to be due to the increased exposure of mucosal tissue to potential infection sites. Transmission risk from infected female to male is around 4–5% annually.[42] Suppressive antiviral therapy reduces these risks by 50%.[43] Antivirals also help prevent the development of symptomatic HSV in infection scenarios, meaning the infected partner will be seropositive but symptom-free by about 50%. Condom use also reduces the transmission risk significantly.[44][45] Condom use is much more effective at preventing male-to-female transmission than vice versa.[44] Previous HSV-1 infection may reduce the risk for acquisition of HSV-2 infection among women by a factor of three, although the one study that states this has a small sample size of 14 transmissions out of 214 couples.[46]
Research has gone into vaccines for both prevention and treatment of herpes infections. Unsuccessful clinical trials have been conducted for some glycoprotein subunit vaccines.[citation needed] As of 2017, the future pipeline includes several promising replication-incompetent vaccine proposals while two replication-competent (live-attenuated) HSV vaccine are undergoing human testing.[citation needed]
Condoms offer moderate protection against HSV-2 in both men and women, with consistent condom users having a 30%-lower risk of HSV-2 acquisition compared with those who never use condoms.[49] A female condom can provide greater protection than the male condom, as it covers the labia.[50] The virus cannot pass through a synthetic condom, but a male condom's effectiveness is limited[51] because herpes ulcers may appear on areas not covered by it. Neither type of condom prevents contact with the scrotum, anus, buttocks, or upper thighs, areas that may come in contact with ulcers or genital secretions during sexual activity. Protection against herpes simplex depends on the site of the ulcer; therefore, if ulcers appear on areas not covered by condoms, abstaining from sexual activity until the ulcers are fully healed is one way to limit risk of transmission.[52] The risk is not eliminated, however, as viral shedding capable of transmitting infection may still occur while the infected partner is asymptomatic.[53] The use of condoms or dental dams also limits the transmission of herpes from the genitals of one partner to the mouth of the other (or vice versa) during oral sex. When one partner has a herpes simplex infection and the other does not, the use of antiviral medication, such as valaciclovir, in conjunction with a condom, further decreases the chances of transmission to the uninfected partner.[14] Topical microbicides that contain chemicals that directly inactivate the virus and block viral entry are being investigated.[14]
