STAT reports:

In an extraordinary time, British health authorities are taking extraordinary measures to beat back Covid-19. But some experts say that, in doing so, they are also taking a serious gamble.

In recent days, the British have said they will stretch out the interval between the administration of the two doses required for Covid-19 vaccines already in use — potentially to as long as three months, instead of the recommended three or four weeks. And they have said they will permit the first dose and second dose for any one person to be from different vaccine manufacturers, if the matching vaccine is not available.

The moves are borne of a desire to begin vaccinating as many people as quickly as possible, particularly with Britain facing high levels of transmission of an apparently more infectious form of SARS-CoV-2, the virus that causes Covid-19.

But they are also effectively turning that country into a living laboratory. The moves are based on small slices of evidence mined from “subsets of subsets” of participants in clinical trials, as one expert described it for STAT, and on general principles of vaccinology rather than on actual research into the specific vaccines being used. If the efforts succeed, the world will have learned a great deal. If they fail, the world will also have gained important information, though some fear it could come at a high cost. [Continue reading…]