The argument is (not sure it’s correct) that since SARS CoV 2 is having it’s first shot at the human immune system (and vice-versa) that the bioengineered mRNA will produce a better or more complete response than people on their own will do.
The phenomenon of wave after wave after wave, with a crash in numbers in the UK and Israel after immunization goes over 55% tends to support this concept.
If you do it, know that the second shot is not recommended for people who have had (proven) COVID, not sure that advice has made its way down to the vaccination centers.
Do you have a professional or personal preference favoring Pfizer over Moderna or vice versa?
My two adult daughters have both been vaxxed, one with Pfizer and one with Moderna. The Pfizer one had markedly more soreness/fatigue with the 2nd dose than the Moderna one did.
They didn’t get to pick and choose since they were in the first wave of medical workers.