Prognosis

Pfizer Backs Two-Dose Shot Schedule as U.K. Spaces Out Shots

  • FDA raises concerns about focusing on single dose like U.K.
  • Pfizer says it’s unknown if protection holds after single dose

A pharmacist administers a dose of the Pfizer-BioNTech Covid-19 vaccine to a resident of a nursing home in the Bronx borough of New York, on Dec. 21.

Photographer: Eric Lee/Bloomberg
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Pfizer Inc. said the second dose of its Covid-19 vaccine should be delivered to individuals within the recommended 21-day period, calling into question a decision by the U.K. to space out the dosing regimen.

The U.K. decision not to hold back any of its vaccine supply is aimed at quickly reaching as many high-risk people as possible. Under the government plan, second doses could be administered as many as 12 weeks later, longer than the three-week timing determined as optimal by Pfizer’s late-stage studies and the four weeks suggested for the shot developed by Moderna Inc.