Study: First COVID-19 vaccination could make subsequent boosters less effective Feb 21, 2023 | coronavirus, COVID-19 Update, Top Stories The original COVID-19 vaccines may hamper the efficiency of booster doses, according to research released by Northwestern Medicine.To access this content, you must purchase 1 Year Health News Illinois Subscription or 1 Year Group Subscription - Up to 5 Users, or log in if you are a member.