News Walgreens to switch second dose of Pfizer COVID-19 vaccine to CDC’s recommended timing April 5, 2021April 5, 2021 Nathan Bomey, USA TODAY Comments Off on Walgreens to switch second dose of Pfizer COVID-19 vaccine to CDC’s recommended timing Walgreens will shorten the window between the first dose of Pfizer's COVID vaccine and the second from four weeks to the CDC's recommended three.