This is good news. If public health authorities are sensible, in view of both the convenience and lower cost, and of the lower efficacy, of the J&J vaccine, they will start parallel vaccination programs: Pfizer and Moderna for over 55s and people with conditions that put them at either severely or moderately increased risk, and J&J for everyone else 18 to 55. (I pick 55 because there's where the case fatality rate jumps up in the by-age data for my county in Kansas.)