The U.K. National Health Service has pushed back the window for people to receive the second dose of the COVID-19 vaccine made by Pfizer and BioNTech — to a duration the companies tested on only a small percentage of patients.
The NHS wrote a letter to hospitals saying those who are scheduled to receive their second dose after Jan. 4 should be rescheduled from three weeks’ time to 12, with most recipients booked in the last week of that time frame. The move would bring the window closer to the time frame for the just-approved vaccine made by the University of Oxford and pharmaceutical company AstraZeneca
The NHS said the move would protect the greatest number of at-risk people in the shortest period and have the greatest impact on mortality.
Confirmed coronavirus cases have spiked over the last month, with the U.K. saying a new variant of the virus that causes COVID-19 is more easily transmissible. Daily cases have climbed from 12,330 at the end of November to 50,023 on Dec. 30.
When the U.K. Medicines and Healthcare products Regulatory Agency gave its emergency approval to the vaccine from U.S. drug company Pfizer
and its German partner
it said the interval between doses must be at least three weeks, and based it on analyses that included patients who received their second vaccination within 19 to 42 days after their first vaccination.
Pfizer said the safety and efficacy of the vaccine hasn’t been tested at the new interval. “Pfizer and BioNTech’s Phase 3 study for the COVID-19 vaccine was designed to evaluate the vaccine’s safety and efficacy following a 2-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,” the company said.
Pfizer also noted there are no data to demonstrate that protection is sustained after 21 days from receiving the first dose.
“While decisions on alternative dosing regimens reside with health authorities, Pfizer believes it is critical health authorities conduct surveillance efforts on any alternative schedules implemented and to ensure each recipient is afforded the maximum possible protection, which means immunization with two doses of the vaccine,” said Pfizer. A message left with BioNTech wasn’t immediately returned.
In the briefing document the drug companies provided to the U.S. Food and Drug Administration, they said about 80% of the patients who received the second dose were administered it within 10 weeks of receiving the first one.