FDA Approves Moderna XFG COVID Vaccines 81 Days Before Teen/Adult Safety Study, 126 Days Before Children’s Study

The U.S. Food and Drug Administration approved Moderna’s new XFG-formulated COVID-19 vaccines on August 27, 81 days before a human study specifically designed to evaluate the safety and immune response of the new formulations was scheduled to begin.

Pfizer’s XFG COVID vaccine formulation was approved on the same day, equally without safety data for its new formulation.

FDA approved the 2026–2027 formulas for Moderna’s SPIKEVAX and mNEXSPIKE vaccines, which are claimed to contain genetic instructions corresponding to the alleged JN.1-lineage XFG subvariant.

But FDA’s own Aug 27 approval letters show that a Phase 3b/4 human study specifically evaluating the “Immunogenicity and Safety of MNEXSPIKE and SPIKEVAX 2026-2027 Formula” is not scheduled to begin until November 16.

The first interim results are not due until March 26, 2027.

For younger children eligible to receive the new SPIKEVAX formulation, a separate human safety and immunogenicity study is scheduled to begin even later.

In other words, FDA approved Moderna’s new XFG vaccines first.

The human studies specifically evaluating the new formulations come afterward.

The regulatory pathway allows FDA to rely on claimed evidence from previously licensed formulations rather than require a new human safety trial of every updated formulation before approval.

But that raises consequential health, informed-consent, regulatory, and accountability questions:

• How can FDA determine that a newly reformulated vaccine is safe before formulation-specific human safety data exist?
• What evidence justifies carrying earlier safety findings forward to a changed product?
• And why is FDA requiring a Phase 3b/4 study specifically to evaluate the new formulas’ “Safety” only after Americans are permitted to receive them?
• And most fundamentally, if FDA is approving a newly reformulated vaccine before human safety data specific to that formulation exist, is the agency fulfilling its responsibility to independently establish that products are safe before Americans receive them, or shifting that uncertainty onto the public and collecting the answers afterward?

Congressional committees have confirmed that the FDA “is not meeting important federal safety requirements to protect its employees and the public while also failing to prioritize scientific data quality delivered from FDA laboratories.”

You can contact the FDA here.

And Moderna here.

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