Opinion: UK decision to delay second Covid-19 vaccine dose is dubious

The rollout of the Pfizer/BioNTech and Moderna Covid-19 vaccines in the US is not proceeding smoothly, which is not surprising given the logistical challenges of administering a novel vaccine that requires two doses. There are similar problems in the UK, where the Pfizer/BioNTech and Oxford University/AstraZeneca vaccines are now authorized, the latter gaining authorization just last week.