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Creech et al. — Evaluation of mRNA-1273 Covid-19 Vaccine in Children 6 to 11 Years of Age

New England Journal of Medicine, 2022 · 10.1056/NEJMoa2203315

OVERSTATED · 4 flags

In plain language

KidCOVE (NCT04796896) randomized 4,016 children aged 6-11 to two 50-microgram Moderna mRNA-1273 shots or placebo (3:1); its two PRIMARY goals were short-term safety and showing the children's antibody levels were non-inferior to young adults' (a surrogate), while Covid protection was only a secondary aim. On its own terms the trial holds up: antibody titers were actually slightly higher than in 18-25-year-olds and cleared the pre-registered non-inferiority margins robustly, and short-term side effects were mostly mild, with every reconciled number reproducing cleanly and no outcome-switching or fabrication found. The famous '88% efficacy' is a secondary result resting on only ~25 mostly-mild, delta-era symptomatic cases over a median 82 days, an absolute risk reduction of about 1.8 percentage points (number-needed-to-vaccinate ~56). The real problem is the abstract's blanket verdict 'safe and effective': with ~3,000 vaccinated children and a short blinded window the trial could not have detected myocarditis at all (it cannot rule out a rate as high as ~1 in 1,000), and it leans on a cross-trial antibody surrogate rather than demonstrated clinical protection. Bottom line: the analyses are honest and correct, but the one-line conclusion overstates what an interim, surrogate-anchored, few-event trial can establish.

Flags — what does not hold up

• moderate overstatement — The abstract's unqualified 'safe and effective ... preventing Covid-19' generalizes far beyond an interim, surrogate-primary, ~25-event, median-82-day readout. Abstract conclusion; primary objectives = safety + immunogenicity immunobridging (Methods); efficacy is secondary.
  integrity moderate · impact high
• moderate conclusion-unsupported — 'Safe' re rare adverse events is not established: with 0 myocarditis in ~2,988 fully-vaccinated children over a short blinded window, the trial had essentially zero power to detect it, so a null count is uninformative. Abstract ('no ... myocarditis ... reported'); protocol/appendix Table S1 (MIS-C/myocarditis pre-specified AESIs with enhanced surveillance); run (rule of three).
  integrity moderate · impact high · recomputed 95% upper bound on myocarditis rate given 0/2988 'none reported' presented as reassuring→~100 per 100,000 (about 1 in 996) one-sided 95%
• moderate overstatement — The headline 88% vaccine efficacy is a secondary, few-event result with a small absolute effect (ARR ~1.8 points, NNT ~56) over ~90 days of mostly-delta symptomatic Covid, which the one-line conclusion does not convey. Figure 3 (CDC def VE 88.0% [70.0-95.8]; incidence 117.1 vs 14.0 per 1000 person-yr; No. at risk 880 vs 2687); run.
  integrity sound · impact moderate · recomputed VE and absolute effect back-out from Fig 3 Poisson CIs VE 88.0% (CDC) / 91.8% (COVE)→VE 88.0/91.8 reproduced; ~18 vs ~7 cases (CDC, ~25 total); ARR 1.78 pp; NNT ~56 70.0-95.8 (CDC)
• moderate conclusion-unsupported — The PRIMARY evidentiary pillar is a non-randomized, cross-trial antibody surrogate (immunobridging vs young adults in a separate trial); clinical protection in children is inferred, not shown, and the surrogate is not validated as a correlate within this trial. Protocol pp.22/100 and appendix p.18 (co-primary GMR/SRR vs Study P301 young adults; NI margin GMR LB>0.67, SRR LB>=-10 and point>=-5); Table 2 (GMR 1.2 [1.1-1.4]; SRR diff 0.1 pp).
  integrity sound · impact high

Method — the checks that were run

• Acquire full text — load_html of PMC9127699 gave abstract/methods/results prose; efficacy method confirmed as mITT1, 14 days post dose 1, exact Poisson.
• Recompute efficacy + absolute effect — run: Byar back-out of Fig 3 Poisson CIs -> ~18 placebo vs ~7 vaccine cases (CDC; ~25 total), ~15 vs ~4 (COVE); VE recomputes to 88.0/91.8, matching the paper; ARR 1.78 pp, RRR 87.3%, NNT ~56.
• Read figures via vision — Fig 1 CONSORT: only 269/997 placebo (27%) and 1907/3005 vaccine (63%) remained blinded at cutoff (heavy EUA crossover). Fig 2: local 'any reaction' 94-95% vaccine vs ~50% placebo = functional-unblinding gradient. Fig 3: efficacy incidence rates and CIs.
• Triangulate registry vs report — Registered co-primaries = safety + immunogenicity immunobridging; Covid efficacy registered AND reported as secondary -> no outcome-switching.
• Read pre-specification — Protocol/appendix: NI margins (GMR lower bound >0.67; SRR diff LB>=-10 and point>=-5) met robustly (GMR 1.2 [1.1-1.4]; SRR diff 0.1 pp); MIS-C and myocarditis/pericarditis pre-specified AESIs with enhanced cardiac surveillance.
• Rare-AE power (rule of three) — run: 0 myocarditis in ~2988 vaccinated -> 95% upper bound ~100 per 100,000; trial powerless to detect the true tens-per-million signal, so the null is uninformative.
• Reconcile SAEs (defuse false alarm) — Blinded Table S21: mRNA 3/3007 vs placebo 2/995 (run RR 0.5), none vaccine-related. Registry full-follow-up: 22/3007 vs 1/995 (run RR 7.28) is an asymmetric exposure-time artifact, not the blinded comparison.
• Denominator census — Safety population 3007/995 vs 'received first injection' 3005/997 = +2/-2 swap consistent with as-treated counting; no undisclosed exclusion.
• COI / provenance — Disclosures list ModernaTX (sponsor, protocol mRNA-1273-P204) plus extensive multi-pharma author grants; abstract foregrounds public funders (BARDA + NIAID). COI is disclosed, not hidden. No retraction/correction/EoC identified.

Next leads — where to look next

• 10.1056/NEJMoa2109522 Ali et al, TeenCOVE - mRNA-1273 in adolescents; same author group and same immunobridging-to-young-adults surrogate as its primary endpoint.
  Its 'safe and effective' claim likely rests on the same surrogate primary plus a rare-AE-underpowered safety set; adolescent males are precisely the myocarditis-risk group this design cannot see.
• 10.1056/NEJMoa2209367 Anderson et al - mRNA-1273 in children 6 months to 5 years, the younger cohorts of THIS SAME trial (NCT04796896; Moderna sponsor, BARDA/NIAID funders).
  The open registry shows even larger follow-up-driven SAE asymmetries (e.g. 45/1994); repeat this audit's blinded-Table-vs-full-registry SAE reconciliation to confirm they are exposure-time artifacts, and re-check the surrogate-primary framing and Moderna's role in AESI adjudication.

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