Should Adults 50+ Wait for Moderna’s mRNA Flu Shot? (mFlusiva/mRNA-1010)

Bottom line: If you’re an adult 50+, the practical move is still to get the currently recommended and available flu vaccine for this season—don’t wait for an investigational candidate you can’t yet choose or receive.

That’s because FDA’s recent advisory committee review of Moderna’s investigational mRNA flu vaccine (mFlusiva/mRNA-1010) is about what the evidence might support for a future FDA decision. It doesn’t mean the product is available for you to pick today.

What FDA’s VRBPAC review does (and doesn’t) mean for patients

On June 18, 2026, FDA convened its Vaccines and Related Biological Products Advisory Committee (VRBPAC) to discuss the benefit–risk assessment for mFlusiva (mRNA-1010), an investigational mRNA-based seasonal flu vaccine candidate, using data submitted to support potential regulatory action. The briefing materials describe this process as an advisory step within FDA’s review—not a final determination or a signal that patients should delay vaccination until after review ends.

What the Phase 3 efficacy signal looked like in adults 50+

In the pivotal Phase 3 study FDA focused on for the ≥50 age group (Study P304), the trial compared mRNA-1010 versus a licensed standard-dose influenza vaccine comparator. Investigators measured RT-PCR–confirmed, protocol-defined influenza-like illness occurring at least 14 days after vaccination through the end of the influenza season.

Overall adults ≥50: The reported relative vaccine efficacy (rVE) was 26.6% (95% CI 16.7% to 35.4%). FDA’s summary indicates this met prespecified success criteria including noninferiority and additional superiority testing in the primary analysis.

Adults 50–64: rVE 26.1% (95% CI 12.3% to 37.7%).

Adults ≥65: rVE 27.4% (95% CI 12.1% to 40.0%), but FDA also highlighted an evidence-context issue: the comparison group for this age stratum was a non-preferential standard-dose comparator rather than the preferentially recommended options FDA described for older adults.

Adults ≥75: The point estimate remained directionally supportive, but the confidence interval was wide and crossed zero—reflecting limited case counts in this smaller subgroup.

What side effects were more common in older adults (and how long they lasted)

FDA’s briefing frames this candidate’s short-term reactions as a reactogenicity pattern that occurred more often than in the comparator group. In Study P304, that shows up as higher rates of solicited local and systemic reactions within 7 days.

Local reactions within 7 days: Any injection-site reaction was reported by 67.5% of mRNA-1010 recipients vs. 32.1% of comparator recipients. Grade 3 local reactions occurred in 1.7% vs. 0.1%.
Systemic reactions within 7 days: Any systemic reaction was reported by 58.0% vs. 32.4%. Grade 3 systemic reactions were 5.5% vs. 0.9%. FDA’s briefing notes no Grade 4 systemic reactions in this comparison.
Median duration (what the briefing summarizes): For mRNA-1010 recipients, the median duration was about 2 days for local reactions (with the comparator at about 1 day). For systemic reactions, the median duration was about 2 days in both groups.
Most frequent systemic symptoms: fatigue (45.1%), headache (37.8%), and muscle aches/myalgia (35.4%).

This matters for the “wait vs vaccinate now” question because it’s part of the benefit–risk tradeoff FDA is evaluating across different older-adult subgroups—not just the average experience of all participants.

Key uncertainties that affect “wait vs vaccinate now”

Even with an efficacy signal, FDA’s briefing materials highlight uncertainties that can matter most for people at the highest risk of severe flu—especially frail older adults.

Efficacy data from one season only: The clinical efficacy evidence was available for one influenza season.
Less direct evidence in immunocompromised and very frail adults: FDA notes efficacy in immunocompromised individuals and very frail older adults “has not been established,” and study exclusion limits how directly results apply to those groups.
Duration of protection: FDA characterizes duration-of-protection evidence as limited in the submitted materials.
Strain-specific precision: For influenza B/Victoria, FDA’s analysis notes a wide confidence interval that crossed zero, driven by limited case accrual.

So the results don’t answer every real-world question—particularly for people whose risk is highest and whose participation in trials may be limited by design.

What readers can do now

Follow CDC’s current flu vaccination guidance for this season. CDC states that everyone 6 months and older should get a flu vaccine each season with rare exceptions, with vaccination particularly important for people at higher risk of serious complications.

For adults 65 and older, CDC lists three preferentially recommended flu vaccine types when available (high-dose, recombinant, or adjuvanted). If none of those preferential options are available at the time of administration, CDC advises getting any other age-appropriate flu vaccine instead of going unvaccinated.

If you’re thinking about “waiting for mFlusiva,” the practical approach is to get an already approved flu vaccine now, and revisit new information only if/when FDA approval and real-world availability become clear.

Quick FAQ

What would change the “get vaccinated now” message?

Most likely: FDA approval and availability of mFlusiva plus clearer evidence that addresses key uncertainty areas—especially performance in immunocompromised and very frail older adults and more complete information on duration of protection.

If mRNA vaccines tend to be better matched, shouldn’t we wait?

Better matching is one potential advantage, but the immediate decision for you is guided by what’s currently approved and available. You can’t benefit from an investigational product you can’t receive yet.

Are the side effects a reason to skip a current flu shot?

In the trial FDA reviewed, short-term reactions were more common with mRNA-1010 than with the comparator, but FDA’s briefing summarizes the reactions as short-lived (median durations ~2 days for mRNA-1010 local/systemic reactions) and also reports longer-follow-up safety outcomes described as balanced between groups. If you’ve had a serious vaccine reaction in the past, it’s reasonable to discuss options with a clinician.

Sources

Editorial note: Weence articles are researched from cited public-health, medical, regulatory, journal, and reputable news sources and may be drafted with AI assistance. They are checked for source support, clarity, and safety guardrails before publication.

This article is for general informational purposes only and is not medical advice. Research findings can be early or incomplete, and health guidance can change. Always talk with a qualified healthcare professional about personal symptoms, diagnosis, medications, vaccines, screenings, or treatment decisions. If you think you may have a medical emergency, call emergency services right away.