The phrase "week intervals" means the time period between one week and the next, usually used to describe something that happens or repeats regularly every week. Full definition
Babies should receive distemper vaccines at 3 - 4 week intervals until age 16 weeks. (healthy-pet.com)
A three to four week interval between vaccinations is ideal. (patrickmahaney.com)
Traditional students start the program in the fall semester, but online students can enroll at eight - week intervals throughout the year. (theemedicalassistants.com)