The booster dose, the FDA said, can come six months after the completion of the two-shot series of both the Pfizer and Moderna vaccines following a review of Emergency Use Authorization approvals for both drugmakers. The FDA approved Pfizer's COVID vaccine, known as 'Comiranty', for booster shots inolder and at risk Americans in late September, one month after asimilar nod for Moderna's in immunocompromised individuals.