At stage 5 he will be needing surgery to fix it. My daughter was not diagnosed untill she was 5 years old. She also has complete duplication of the ureters, enlarged bladder, enlarged kidneys, voiding disorder and had stage 3/4 reflux in the left side. For a year we tryed the antibiotics, but she had repete infections. We chose the DEFLUX procedure for her VUR and it has worked great, she is now 8 years old and has only had a few UTI's. But at stage 5 VUR your son will require the traditional surgery, deflux is not an option with that severe reflux.
This is an awesome web site that will give you tons of great information:
http://www.deflux.com/Deflux.aspx?id=101
My girlfriends daughter was diagnosed at age 2 with stage 5 reflux and she had the traditional surgery, she is now 8 years old and has never had another UTI. I know it sounds super scary to think your baby is so young going in for surgery, but the younger the better!! He will have little to no damage done to his kidneys from the reflux and will not remember the surgery. My little girl has some pretty bad scaring of her kidneys from going undiagnosed and having so many UTI's over the years. And remembers going to the hospital. Think of it as a blessing that you found out early enough to fix it right away! If your in the Phoenix AZ area recomend Dr. Michael Nuygen. He is contracted through Phoenx Childrens Hospital. Best of Luck!!!!