Similar to a situation where a medical professional is stuck with a needle. A prophylactic treatment is to start HIV prevention drugs within 24 hours; such as Viread to stop the virus from entering the body and cure the issue. Now regarding herpes, if someone suspects herpes exposure, if I were to start on Valtrex within 24 hours, would this stop the virus from spreading or in other words kill it as so it cant spread any further. Same goes for taking Doxycycline stop all bacterials in there tracks prior to manifestation. Thanks