Pfizer's booster is for people who got Pfizer: All about mixing COVID-19 vaccines - CNET[ Fri, 24 Sep 2021 15:04:18 +0000 ]A large swath of the country who've received Pfizer's COVID-19 shots are eligible for a booster. But if you got Moderna or J&J, there isn't enough data to OK mixing COVID-19 vaccines.