First doses of Pfizer/Moderna vaccines are 90%+ effective after 14 days. Most high risk lives will be saved by giving all these limited early supplies of vaccine as first doses – second doses can be given later if first dose effectiveness wanes or when supply improves
Here’s a way of thinking about this policy. Suppose you are scheduled for your second dose of the Pfizer or Moderna vaccine but you have the option of giving your second dose to your spouse as their first dose. Would you?
If the answer is yes then can you ethically deny this to someone else’s spouse?
Keep in mind that we have at least three more vaccines that could be available in as little as 12 weeks, Astra-Zeneca, Johnson & Jonson and Novavax. We are also pushing for more doses from Pfizer and we should be willing to pay top-dollar for those doses. As those vaccines come online we can deliver second doses.
Addendum: If you are 75 and your spouse is 25 then maybe you wouldn’t give your second dose to your spouse and that too ought to help us think about the larger questions of allocation.