Just to clarify, the report isn't saying 9.3% of all adolescent vaccinees experienced serious events. It's 9.3% of the reports, which is a huge difference. This excerpt may provide additional context for folks:
"Among 8.9 million adolescents vaccinated during the study period, VAERS reports were received for approximately one per 1,000 vaccinees, and 90% of these reports were for nonserious conditions."
So essentially, 0.01% (or one in 10,000) of the study group vacinees during the study period reported "serious" symptoms, which by their account includes headache, fever, nausea, etc.