I called the SPCA to make an appointment for my 16 week old puppy's third set of shots . They informed me that they will not give vaccinations unless the dog is spayed , and gave me an appointment to have her fixed . August 14th . At this time , she'll be 18 weeks . 
Question: What may be the SPCA's reason for not vaccinating your dog ?
Its genitals needed to be removed first .