J&J was removed from the market because of side effects. I don’t know about Novavax. I was thinking of getting that once upon a time until I contracted Covid. No way I’m taking any shots now.
There are several advantages to J&J : 1 shot, no boosters ; refrigeration only, no freezer storage ; same efficacy at preventing serious Covid/hospitalization as Pfizer-BioNtech/Moderna with less frequency of side effects.
It was allowed to expire because the company didn’t contribute politically to the Trump campaign at the levels of Pfizer and Moderna.