Nation Pfizer vaccine 93% effective at keeping adolescents 12-18 out of the hospital, CDC says: COVID-19 updates October 19, 2021October 19, 2021 Celina Tebor and Ryan W. Miller, USA TODAY Comments Off on Pfizer vaccine 93% effective at keeping adolescents 12-18 out of the hospital, CDC says: COVID-19 updates The Pfizer vaccine was highly effective on teens even in the throes of the summer spike in COVID cases from the delta variant. Latest updates.