About half of all patients who require intensive care will likely need a ventilator to survive, health experts said. The Harvard study estimated that if 40% of a population is infected over the course of six months, about 80% of people under age 65, and 71% of those over that age, will recover without hospitalization, but about 12,300 Pennsylvanians and 8,300 Garden Staters, at peak times during that six-month period, will require ICU treatment.