Reanalysis of FDA Clinical Data for mFLUSIVA (mRNA-1010)

Background/objectives: On 5 August 2026, the FDA approved Moderna’s mFLUSIVA (mRNA-1010) for adults aged ≥50 years, granting Traditional Approval for ages 50–64 years based on clinical efficacy and Accelerated Approval for ages ≥65 years based on hemagglutination-inhibition titres. We reassessed the evidentiary basis for licensure on an absolute benefit–risk scale.

Methods: FDA regulatory and clinical-trial data were reanalyzed using absolute risk differences, numbers needed to vaccinate (NNV), numbers needed to harm, unadjusted risk ratios (RRs) with 95% confidence intervals (CIs), and harms incurred per clinical benefit obtained.

Results: Neither pivotal trial included a placebo arm. Every solicited adverse reaction was more frequent with mFLUSIVA than with the standard-dose comparator. Overall solicited adverse reactions occurred in 75.7% of mFLUSIVA recipients versus 46.7% of comparator recipients, and Grade 3 systemic reactions occurred in 5.5% versus 0.9% (RR, 6.15; 95% CI, 4.11–9.20). Unexplained deaths occurred in 23 mFLUSIVA recipients versus 9 comparator recipients (RR, 2.55; 95% CI, 1.18–5.52), increasing to 29 mFLUSIVA recipients versus 12 comparator recipients when related fatal-event terms were pooled (RR, 2.42; 95% CI, 1.23–4.73). Only one autopsy was performed across the clinical program, in the comparator arm. Relative vaccine efficacy against RT-PCR-confirmed influenza-like illness was 26.6% (95% CI, 16.7–35.4). The NNV was 137 for one confirmed illness, 1003 for one higher-level-care encounter, and 5017 for one hospitalization. Per hospitalization averted, approximately 1454 additional solicited adverse reactions, 233 additional Grade 3 systemic reactions, and 2 excess unexplained deaths were observed. No influenza-mortality endpoint was specified, collected, or reported.

Conclusion: mFLUSIVA demonstrated minimal absolute clinical benefit while producing substantially greater reactogenicity and a significant unresolved mortality signal. The extreme risk-benefit profile does not support continued licensure of mFLUSIVA and supports reconsideration of its market authorization.

Keywords: mRNA vaccine, mFLUSIVA, regulatory science, influenza, risk-benefit analysis