2 +1 = more sales.

$Pfizer (PFE.US)$ - Booster COVID-19 vaccine shots give an estimated 70% to 75% ....

If you focus on the % , you might want to consider the below point.

now boosters are a 'required' shots. The new basic shots just upgraded from 2 shots to 3 shots. it doesnt take a genius to understand that periodical shots are strongly required.