I think you missed the point of the article, it sounds like propaganda to get people to submit to the vaccine. They are 'claiming' that UNVACCINATED people are getting sick in HUGE numbers, way too many to be infected by the small numbers of people of who have got vaccinated already so I reckon it's BS article?
"Hospitalization rates among Michigan adults who haven't received their COVID-19 vaccines are increasing at an "alarming rate," "From March 1 to Wednesday, March 23, hospitalizations increased by 633% for adults ages 30-39 and by 800% for adults ages 40-49, the association said in a statement."