The only argument for First Doses First (FDF) is that 2*0.8>.95, i.e. two vaccinated folks confers extra immunity than one double vaccinated individual. However there’s extra to it than that. Maybe extra vital is that with FDF we’ll decrease R extra shortly and attain herd immunity sooner. Right here’s an excessive however telling instance.
Suppose you’ve a pop of 300 million, want 2/3 to get to herd immunity and you’ve got 100m doses and might vaccinate 100m a month. Then with FDF you vaccinate 100m in first month and a brand new 100m within the second month after which you’re “carried out.” i.e. you possibly can then do 2nd doses kind of at leisure since you’re at herd immunity (sure, I find out about overshooting, it is a easy instance). If as a substitute you do second doses you vaccinate 100m in first month and the identical 100m within the second month which leaves 100 million in danger for an additional month. Beneath second doses you don’t attain herd immunity till the third month. Thus, below FDF you save a 100m infection-month which is a giant deal.
Now if you put this right into a extra refined SEIR mannequin you gained’t get as sturdy a outcome however the outcome can be in the identical route. Notice additionally that attending to herd immunity sooner might be the perfect factor we are able to do to stop additional mutations.
See additionally Youyang Go’s thread the place he discusses his modeling of comparable concepts. He notes:
Reaching herd immunity two or three months sooner may have profound advantages all through society, starting from fewer circumstances & deaths to sooner financial restoration.
Addendum: Please learn Tyler’s publish, FDF?-Show Your Work! earlier than you remark.