London, Jan 1 : The UK's chief medical officers have defended the Covid vaccination plan, after criticism from a doctors' union.
The UK will give both parts of the Oxford and Pfizer vaccines 12 weeks apart, having initially planned to leave 21 days between the Pfizer jabs, the BBC reported.
The British Medical Association said cancelling patients booked in for their second doses was "grossly unfair".
But the chief medical officers said getting more people vaccinated with the first jab "is much more preferable".
The Pfizer-BioNTech vaccine was the first jab approved in the UK, and 9,44,539 people have had their first jab.
The first person to get the jab on December 8, Margaret Keenan, has already had her second jab.
Pfizer has said it has tested the vaccine's efficacy only when the two vaccines were given up to 21 days apart.
But the chief medical officers said the "great majority" of initial protection came from the first jab.
"The second vaccine dose is likely to be very important for duration of protection, and at an appropriate dose interval may further increase vaccine efficacy," they said.
"In the short term, the additional increase of vaccine efficacy from the second dose is likely to be modest; the great majority of the initial protection from clinical disease is after the first dose of vaccine."
The decision to delay the second dose has, understandably, caused concern.
There is some evidence regulators say - at least for the Oxford vaccine - that it will actually boost immunity.
But for those who are due to get a second dose soon it will undoubtedly be upsetting that they now have to wait.
But the move is about practicalities.
The UK is in the middle of a public health crisis and despite the fact that millions of doses are pre-ordered, there is concern the supply of the vaccine will not be as smooth as everyone would ideally want.
There is a global demand for these vaccines and there are bound to be times when supply does not meet demand.
So the logic of the move is that by spreading this thin resource the most widely, it will have the greatest benefit - not only to the vulnerable but to everyone.
Lives have been put on hold and livelihoods lost.
This is the quickest way back to some degree of normality.
Even if it does leave some of the vaccinated susceptible to infection, it should in theory at least protect them from serious illness.
Given where we are now, the argument is that that is a price worth paying.