The gap between the first and booster doses of Pfizer (NYSE:PFE) and BioNTech's (NASDAQ:BNTX) coronavirus vaccine has been widened substantially in the U.K. -- and Pfizer is not pleased about it.

The U.K.'s joint committee on vaccination and immunization, an advisory body that advises government healthcare agencies, approved new dosing guidelines for both Pfizer/BioNTech's BNT162b2 and the just-approved AZD1222 from AstraZeneca and the University of Oxford. The new guidelines state that both vaccines' two requisite shots can be administered as much as three months apart.

The key aim of the new recommendation appears to be to get as many people inoculated as possible with the initial shot. Research indicates that partial protection against the coronavirus can start as soon as 12 days after the first jab.

A syringe being filled with a vaccine from a vial.

Image source: Getty Images.

However, according to the Financial Times, Pfizer said, "[Our] study ... was designed to evaluate the vaccine's safety and efficacy following a two-dose schedule, separated by 21 days ... The safety and efficacy of the vaccine has not been evaluated on different dosing schedules, as the majority of trial participants received the second dose within the window specified in the study design." 

It also said that there is no data indicating the vaccine's initial dose is effective after those 21 days.

The changed recommendation has caused some turmoil in the country, the FT wrote. Doctors have been forced to rework scheduling for patients aiming to return several days after their initial shot for a booster. The newspaper quoted Dr. Helen Salisbury, a general practitioner in Oxford, as saying that the situation was "a shambles."

Neither Pfizer nor BioNTech outperformed the S&P 500 index on Thursday. The former company's stock inched up by only 0.2% on the day, while the latter's fell by 2.9%.

 
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