They phrased it that way because the FDA did. Without any legal basis as it seems.

Moderna said the FDA reviewed and accepted its trial design on at least two occasions (in April 2024 and again in August 2025) before it applied for approval of mRNA-1010. It also noted that Fluarix has been used as a comparator vaccine in previous flu vaccine trials, which tested vaccines that went on to earn approval.

But in a letter dated February 3, Vinay Prasad, the FDA’s top vaccine regulator under the Trump administration, informed Moderna that the agency does not consider the trial “adequate and well-controlled” because the comparator vaccine “does not reflect the best-available standard of care.”