The approval was based on the late-stage FLUENT trial, which randomly assigned more than 40,000 adults 50 and older across 11 countries to receive either the mRNA vaccine or a licensed standard-dose comparator. The mRNA shot showed roughly 27% greater effectiveness than the standard vaccine. Side effects, including injection-site pain, fatigue and headache, were more common in the mRNA group than among those who received the standard shot, though researchers characterized most as mild to moderate and transient. The approval arrives despite repeated public criticism of mRNA vaccine technology from Health and Human Services Secretary Robert F. Kennedy Jr., who canceled 22 mRNA vaccine development projects last year. Continued monitoring of the vaccine's regulatory progress in Europe, Canada and Australia, along with how the Trump administration's broader stance on mRNA technology shapes future vaccine approvals, is expected to remain a relevant thread in the coming months.