. Beginning in August, a half-dozen researchers at a Pfizer lab in Massachusetts sat down with vials of experimental coronavirus vaccine to learn how to transform the "overfill" in every vial — an extra amount of liquid that is standard for injectable pharmaceuticals — into a precious sixth dose. Over the next few months, they tested dozens of different combinations of syringes and needles, drawing out vaccine and squirting it into a beaker resting on a digital scale,repeating the experiments 5 to 10 times for each. By Jan. 6, the work paid off. Pfizer won approval from the Food and Drug Administration to say its vials contained six doses, instead of the five the agency had approved less than a month earlier with its Dec. 11 emergency authorization of the vaccine.