It happens all the time. They just combine a number of vaccines into a single shot. Pediatricians tend to get angry if you ask them to spread them out over a longer period of time. Personally, I believe that is a contributing cause to the rise in autism and ADHD. Researchers try to pin it to a single vaccine, but I believe it is the NUMBER of vaccines received, not necessarily a single one, although some parents believe it is the MMR (3 vaccines). Every parent I know who has an autistic child relates it to a vaccine occurrence. I know one child who developed cerebral palsy after a vaccination. She was absolutely normal prior to that.