The parent comment wondered > whether Johnson & Johnson and AstraZeneca are meaningfully different Grammatically, that asks about the difference between J&J &

The parent comment wondered > whether Johnson & Johnson and AstraZeneca are meaningfully different Grammatically, that asks about the difference between J&J & AZ. Your response instead compared them collectively to the mRNA vaccines, rather than comparing them to each other. Thus the response saying "[t]hat’s not the difference the parent is asking about."