Doctors from the British Medical Association (BMA) are urging England's chief medical officer to "urgently review" plans to allow a 12-week gap between the first and second doses of the Pfizer/BioNtech coronavirus vaccine.
UK government officials had said that second doses would be scheduled 12 weeks after the first doses, even though in the vaccine trial, doses were given three weeks apart.
Pfizer and BioNTech had warned the safety and efficacy of the vaccine had not been tested on different dosing schedules.
A spokesperson for the medical association said in a statement provided to Euronews that the BMA supported giving a second dose up to six weeks after the first dose, "in line with international best practice," because it would allow twice the number of people to be vaccinated.
But, the BMA spokesperson said, "the UK’s strategy has become increasingly isolated from many other countries."
The European Medicines Agency has recommended a six-week gap between the first and second doses of the Pfizer vaccine, which experts say is supported in the trial study.
The World Health Organisation, meanwhile, recommends that second doses of the Pfizer/BioNTech vaccine should be given within three to four weeks of the first dose.
"WHO has said that in exceptional circumstances this might be extended to within 42 days (six weeks) and there appears to be evidence for this in the Pfizer-BioNTech trial. However, the UK’s delay to 12 weeks goes well beyond even this timeline," a BMA spokesperson said.
Other countries had also investigated extending gaps between doses in an effort to vaccinate more people up front.
The US Food and Drug Administration had said in early January that changing the dosing schedule was not supported by "adequate scientific evidence."
But the US Centres for Disease Control and Prevention has since said that "the second dose of Pfizer-BioNTech and Moderna COVID-19 vaccines may be scheduled for administration up to 6 weeks (42 days) after the first dose."