Using a narrow needle to administer coronavirus jabs significantly boosts supply of the vaccine, officials have announced.
Drawing the liquid drug out of a vial using a syringe with less "dead space" increases the number of doses available by up to 20 per cent, according to Public Health England.
Dr Mary Ramsay, the organisation's head of immunisations, said staff had been able to get at least one more dose out of vials for both the Pfizer and AstraZeneca jabs.
However, she said the additional capacity had not been factored into the national rollout plans, suggesting the forecast deliveries of jabs could immunise more people than planned.
The Medicines and Healthcare products Regulatory Agency, which approved the two vaccines, was reportedly consulted on the issue and has "raised no objections".
Addressing the science and technology select committee, Dr Ramsay said: "By using what's called low dead space needles, we have been able to get more vaccine out of each vial, and that's happened for the Pfizer vaccine and it's also happening for the AstraZeneca vaccine. So that means that overall we've got more vaccine to go round, so that's really good."
Dr Ramsay added that staff had been using the narrower needles from the start of the rollout.
Doctors and nurses are routinely able to get a sixth dose out of the Pfizer vials, which are supposed to contain five, and an extra dose out of both the AstraZeneca eight and 10-dose vials.
Dr Ramsay said the practice was commonplace but not uniform because it partly depends on the individual technique of drawing the vaccine.
The extra doses were confirmed later in the hearing by Nadhim Zahawi, the minister for vaccine deployment, who also said wastage of doses – for example due to breaks in the cold chain – were "much less" than the 10 per cent predicted by NHS England.
Mr Zahawi promised the committee that "by the end of the month we'll be able to deploy two million a week, and then we keep going".
Meanwhile, the chair of Covid-19 immunisation at the joint committee on vaccination and immunisation defended the science behind the decision to delay the second dose in order to protect more people with the first.
Professor Wei Shen Lim said that overall in the Oxford-AstraZeneca trial, which took place in multiple countries, over 60 per cent of participants got their second dose after six weeks. In the UK arm, one third of those got it after 12 weeks.
He said that those in whom the drug had shown higher efficacy it had done so because they received the second dose later and not because their initial jab was a half dose, as was thought when the results were first made public in November.