Why is there a difference in the vaccine schedules given by my GP and at work?

Hi doctor,

I am a nursing student studying outside. I have just moved over from my hometown. Because I am doing nursing, the hepatitis B vaccine is required for occupational health. I received my first vaccine in January, followed by my second in February, from my own GP back home. He told me the next (third) vaccine would be due in August. However, when I started my nursing course (in February), we all had to meet with the occupational health team. I showed her my records for hepatitis B, and she told me that the third vaccine was due in March, just a month after my second one. I was just wondering why is there such a difference in the times given between my own GP and the occupational nurse. I looked it up online, and going by that, my GP's time allocations for the vaccine seem right, but is the occupational health one correct as well? Thanks for the help.