Valtrex is strictly for the person who has herpes. There is no drug available as a preventative for someone who's herpes negative.
You can read more about genital herpes, and watch a counseling video here at this website:
http://www.westoverheights.com/genital_herpes/handbook/view_the_chapters.html
Thank you petal130, this is really, really useful info. Random question - is there any advantage/extra protection for the partner NOT infected to go on suppressive therapy as well such as Valtrex?
It's up to you, but I can't imagine ending a relationship based on herpes. There are so many other things that can send a relationship south, and managing herpes is an easy one. It's nothing more than a pesky skin condition.
Here are the stats for male to female transmission rates:
MALE TO FEMALE TRANSMISSION RATES (HSV 2 ONLY STATS IS NOT APPLICABLE FOR HSV 1) If you have 100 couples where the male has HSV 2 but not the female (these figures are over a year) the odds of male to female transmission are if you do nothing (other than avoid sex when there is an outbreak) 8-10 females out of a 100 will get herpes in a year, or 8-10%. If you do go on a suppressive therapy then it drops to 4-5 females out of a 100 in a year or 4-5%, and if you use suppressive therapy and a condom the chances are 2-3 females out of a 100 will get herpes in one year, or 2-3%.
The Valtrex and transmission study stats are based on having sex 2 times/week.