He said that before Christmas, only a “handful of health and social care workers and some over 70s” will face the dilemma. But numbers will grow in the new year as more people have access to jabs via the NHS.
Meanwhile a Pfizer spokeswoman said the company “would have an ethical responsibility to inform all study participants about the availability of an emergency authorised vaccine by the Food and Drug Administration [FDA].”
The Pfizer vaccine was approved by the UK regulator, the MHRA, this week, but there have been no UK trials for this jab.
There have been studies in the United States, where the regulator, the FDA, is still reviewing the vaccine. It is understood that FDA would make a recommendation on when to unblind the trial – though they could remove the placebo arm and continue to monitor those who receive the vaccine.
Pfizer has reportedly also proposed to regulators that any volunteers who received the placebo should be offered the real vaccine when the study concludes.
Many, however, remain adamant that the benefits of continuing control trials far outweigh the risks.
On Wednesday 18 members of a World Health Organization panel, called the ad hoc expert group on the next steps for Covid-19 vaccine evaluation, made the case for placebo-control groups in the New England Journal of Medicine.
“After relatively short follow-up in phase 3 trials, even when vaccine efficacy appears to be high, reliable information will still be needed on longer-term safety and duration of protection,” the team wrote.
“[The] opportunity to obtain reliable evidence about longer-term effects would be destroyed by early unblinding and immediate vaccination of participants assigned to placebo.”