Hi & Welcome. Valtrex (valacyclovir) is an antiviral drug. It works by slowing the growth and spread of the herpes virus to help the body fight the infection. It is commonly used to treat infections caused by herpes viruses, including genital herpes, cold sores, and shingles (herpes zoster) in adults. Valtrex will not cure herpes infection and will not prevent you from spreading the virus to other people. However, this medicine can lessen the symptoms of an infection. Based on the history you seem to have developed recurrent cold sore, continue taking Valtrex as prescribed by your doctor. Hope this will help.