Flu Season's Toll: 166 Deaths and What's Next

The 2025–26 flu season is over in any practical sense — flu activity is now at minimal levels across all 54 reporting jurisdictions. 1 But the numbers it left behind are hard to set aside. While you're planning summer, it's the right moment to understand what this season actually showed — and what that means for your family's decisions this fall.

The season hit children especially hard

The final Week 18 FluView report (data through May 9, 2026) put the season total at 166 influenza-associated pediatric deaths — 8 new ones reported that week alone. 1 That number ranks among the highest non-pandemic pediatric death tolls since the CDC began tracking in 2004.

The detail that should stay with parents: among children who were eligible for vaccination and whose vaccination status was known, approximately 85% of those who died had not been fully vaccinated against flu. 1 That figure has stayed consistent throughout the season.

Overall, the CDC estimates this season caused at least 32 million illnesses, 380,000 hospitalizations, and 24,000 deaths across all ages. 1 The cumulative hospitalization rate reached 86.3 per 100,000 people — highest among adults 65 and older (275.3 per 100,000) and children under 5 (97.6 per 100,000). 1 The CDC classified the season as moderate overall but high severity for children specifically — a distinction that rarely gets the attention it deserves in headlines that tend to talk about "average" severity.

One more wrinkle: by Week 18, influenza B/Victoria had overtaken influenza A/H3N2 as the dominant circulating strain (63.8% of positives at public health labs). 1 If your child caught flu earlier in the season — when H3N2 was dominant — they haven't necessarily built immunity against B/Victoria. That strain tends to hit children harder than adults.

CDC preliminary estimated flu disease burden for the 2025–26 season

Image from: CDC NCIRD — Preliminary Estimated Flu Disease Burden 2025–2026

The vaccine worked — just not as well as it should have

This season's flu shot offered real but reduced protection, and the reason is specific: the dominant H3N2 strain mutated away from the vaccine. Only 1.5% of H3N2 viruses tested in Week 18 were antigenically well-matched to the vaccine reference strain — a near-total mismatch. 1 By contrast, 98.8% of H1N1 viruses matched well.

The result showed up in effectiveness numbers. CDC's interim estimates (data through February 2026, published in MMWR): 2

Population	Outpatient protection	Hospitalization protection
Children & adolescents (6 months – 17 years)	38–41%	41%
Adults 18 and older	22–34%	30%

Even against a mismatched strain, getting vaccinated cut hospitalization risk by 30–40%. 2 That's not a great headline, but it's a meaningful number when you're looking at a season that put 380,000 people in the hospital.

For adults 65 and older: a May 2026 meta-analysis of 586,188 participants found that high-dose flu vaccines (Fluzone HD) cut influenza-specific hospitalization by 39% compared to standard-dose shots. 3 A separate JAMA Network Open study (May 4, 2026, 429,595 older adults) found adjuvanted vaccines (Fluad) performed equally well as high-dose shots. 4 Bottom line for seniors: either Fluzone HD or Fluad is meaningfully better than a standard-dose shot, and the data supports either choice.

Despite all of this, vaccination rates barely moved. As of May 2, 2026, only 49.2% of children and 46.5% of adults were vaccinated this season. 5 6 Pregnant women — a high-risk group — reached only 37.7% coverage, essentially flat from last year. 5 The racial disparities are stark: among pregnant women, non-Hispanic Asian women had 53.0% coverage while non-Hispanic Black women had 25.5% — a 27.5-percentage-point gap. 5

The mRNA flu vaccine is coming — but not this year

The biggest piece of longer-term news this week: Moderna published Phase 3 trial results for its investigational mRNA flu vaccine, mRNA-1010, in the New England Journal of Medicine (May 6–7, 2026). 7

The trial enrolled 40,703 adults aged 50 and older across 11 countries during the 2024–25 flu season. 7 Participants received either mRNA-1010 or a licensed standard-dose flu shot. The mRNA vaccine showed 26.6% greater relative efficacy (95% CI: 16.7%–35.4%) — fewer flu cases in the mRNA group (2.0% vs 2.8%), meeting the trial's criteria for superiority. 7 Among participants 65 and older, relative efficacy was 27.4%. 7

Side effects were more common with mRNA-1010: injection-site pain (65.8% vs 29.8%), fatigue (45.1% vs 20.3%), and muscle aches (35.4% vs 11.6%). Most were mild to moderate and resolved within a few days. 7 No cases of myocarditis or pericarditis were detected within the 42-day risk window. 7

A Moderna researcher in a laboratory setting, examining a multi-well plate

Image from: Moderna, Inc. — NEJM Publication Announcement

The regulatory path has been turbulent. On February 3, 2026, FDA's Center for Biologics (CBER) issued a Refuse-to-File letter rejecting even a review of Moderna's application — not because of safety or efficacy problems, but because the trial used a standard-dose comparator while FDA guidelines recommend high-dose or adjuvanted shots for adults 65+. 8 Moderna went public with the letter — unusual, since these letters are normally confidential — and pushed back, arguing the comparator had been pre-agreed with CBER before the trial started. 8

About a week later, the FDA reversed course and agreed to review the application, setting an August 5, 2026 PDUFA target date — the deadline by which the agency must complete its review. 9 A PDUFA date is not a guaranteed approval; it's a review deadline. The FDA also required Moderna to conduct an additional study. On May 12, FDA Commissioner Marty Makary resigned, leaving CBER in a leadership transition. 10

The key caveats families should understand:

mRNA-1010 is not available for the current season. No US approval exists.
The trial did not compare mRNA-1010 against high-dose or adjuvanted shots — the formulations already recommended for adults 65+. Whether mRNA-1010 is better than Fluzone HD or Fluad for seniors is still unanswered. 7
The trial enrolled only adults 50 and older. No pediatric data exists.
Earliest possible US availability: fall 2026, if FDA approves by August 5 and ACIP issues a recommendation in time for manufacturing. Both are uncertain given the ongoing FDA leadership transition.

Pfizer's mRNA flu vaccine (PF-07926307) remains in Phase 2, with no new announcements between May 5–17, 2026. 11

What the research journals published this week

A fatal bird flu case in Washington state — and why it went undetected. A May 7 NEJM case report described a 75-year-old woman in Washington state with a blood cancer (Waldenström macroglobulinemia) who died from HPAI A(H5N5) avian influenza — a strain of bird flu not previously reported in a US human. 12 She had daily contact with backyard ducks, had not received the flu vaccine, and presented with fever and diarrhea. Multiple nasal swabs came back negative for influenza A. The virus was only detected — on day 15 of illness — through a bronchoscopy lung wash (bronchoalveolar lavage). She died on day 28. 12

The case has two practical implications. First, for anyone with backyard poultry: standard flu swabs may miss avian influenza, especially in immunocompromised people. If you or a family member has close poultry contact and develops severe respiratory illness, tell your doctor. Second, no transmission to household contacts or healthcare workers was detected, 12 which is reassuring — this was a case of direct bird-to-human transmission, not person-to-person spread.

Vaccine immune memory is more durable than most people assume. A comprehensive review published in Immunity (Cell Press, April 14, 2026) by Shane Crotty at the La Jolla Institute for Immunology found that B-cell immune memory from vaccines can persist for more than 60 years — researchers identified 1918 pandemic flu B-memory cells in people in their 90s and 100s in 2008. 13 The review also clarified why FluMist (the nasal spray flu vaccine) has been frequently underestimated: it builds local immune memory in the upper airway tissues that injectable shots don't reach, but that local memory doesn't show up in standard blood tests — leading to years of misleading data suggesting it wasn't working in adults. 13 For families with children who use FluMist: the protection it builds in the airway is real, even if it's invisible on a blood panel.

What families should do right now

If flu activity is low, why act now? Because fall vaccine decisions get made in the next few months — by manufacturers, regulators, and your own family — and this season has clarified some of the key variables.

Check which vaccine schedule your pediatrician is following. In January 2026, the CDC revised its childhood immunization schedule, reportedly removing flu vaccine from the universal child recommendation. The American Academy of Pediatrics (AAP) released its own 2026 schedule that still recommends flu vaccination for all children. A March 16, 2026 federal court stay (in AAP v. Kennedy) paused the CDC's revised schedule pending litigation, and the government filed its appeal on May 7 — 52 days late. 14 Most pediatricians are using AAP guidance, which maintains the flu vaccine recommendation. Confirm this with yours.

If you're 65 or older, ask specifically for Fluzone HD or Fluad. The evidence from both a 586,000-person meta-analysis 3 and a JAMA study of 429,595 older adults 4 supports these over standard-dose shots for adults 65+. Either option is appropriate — the data does not favor one over the other.

Don't wait for mRNA-1010. The earliest it could be available in the US is fall 2026, and that depends on FDA approval by August 5, an ACIP recommendation, and manufacturing scale-up — all of which face uncertainty. The standard-dose shot available today is the right choice for the current season and for fall planning unless the picture changes substantially by August.

Watch for the ACIP June meeting. The Advisory Committee on Immunization Practices (ACIP) — the expert panel that recommends which vaccines Americans should receive and at what ages — meets June 24–26, 2026. 15 The committee is expected to discuss the composition of the 2026–27 flu vaccine. Given how badly H3N2 matched this season, strain selection for next fall will be a critical agenda item.

Cover image: CDC FluSight — National Forecast of New Influenza Hospital Admissions, as of May 6, 2026