to those wondering about the question over why a vaccine at:
full dose and a booster 3 weeks later at full dose
does not result in as good effect vs
half dose and a booster 3 weks later at full dose.

..
well its like a car with 'turbo' if the turbo only kicked in when the car was at full revvs the car would just give up and not want to go faster.
but when you set a turbo to kick in at half revs you get a true boost. which then helps your car achieve even greater speeds.
..
its like eating a full meal. and then trying to squeeze in a dessert. just leaves you feeling sluggish.
but if you have a light meal and then a big dessert. you are happy and more energised.

trying to stretch a system while its already at its peak. wont make it want to stretch further.
but letting it stretch while its still has potential makes it go beyond the first limit

try to run full speed in a 200m sprint.. your body wont like it and want to stop before you get to the finish
then try to jog for 100m then sprint the last half. you will get to the finish line in better condition

hope you now understand how real life works.