I’m unclear why blinding is critical. It should have almost no effect on safety evidence. It seems likely to have a moderate effect on the quality of the efficacy evidence. But the harm from delaying vaccines for a few weeks seems a good deal larger than the harm from not having ideal information about which vaccine is most effective.
Alex Tabarrok has some related discussion in How to Vaccinate and Continue Clinical Trials.
I’m unclear why blinding is critical. It should have almost no effect on safety evidence. It seems likely to have a moderate effect on the quality of the efficacy evidence. But the harm from delaying vaccines for a few weeks seems a good deal larger than the harm from not having ideal information about which vaccine is most effective.