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A newly publishedNew England Journal of MedicinePhase 3 trial has confirmed that Moderna’s experimental mRNA seasonal influenza vaccine, mRNA-1010, caused severe short-term reactions at roughly six times the rate of standard-dose flu shots while delivering less than a 1-percentage-point absolute reduction in symptomatic, PCR-confirmed influenza-like illness.
The study found that recipients of the mRNA flu shot experienced dramatically more severe short-term side effects, while the overall difference in influenza illness between the two groups remained small.
The trial, published on Thursday, evaluated more than 40,000 adults aged 50 and older across 301 clinical sites in 11 Northern Hemisphere countries during the 2024–2025 influenza season.
The new study compared Moderna’s trivalent mRNA-1010 shot against licensed standard-dose influenza vaccines, not the enhanced high-dose, adjuvanted, or recombinant flu vaccines already recommended for many older adults.
That distinction is important because the study did not prove Moderna’s shot performed better than the said-to-be strongest influenza vaccines currently available for seniors.
Instead, it showed alleged superiority only against older standard-dose flu shots.
Researchers reported that PCR-confirmed, protocol-defined influenza-like illness occurred in 2.0% of mRNA-1010 recipients compared with 2.8% of standard-dose flu shot recipients—a 0.8-percentage-point absolute difference that the paper framed as 26.6% relative vaccine efficacy.
For the average reader, that means the “26.6% better” headline sounds much larger than the actual real-world difference observed in the study population.
More than 97% of participants in both groups did not develop the study’s primary endpoint.
Source: modernity
