2026-2027; The Coming Flu Season
What the Southern Hemisphere has already told us, what New Mexico did last winter, and how to choose a vaccine
The view from the south
Flu travels by hemisphere. Australia and New Zealand take their winter while we take our summer, and the viruses that trouble them in July reach us by December. This gives us a few months' warning about which viruses are coming. It tells us nothing, however, about how bad they will be. Forecasting models lose their footing past four weeks, so anyone who tells you in September how bad February will be is guessing.
Last year the warning mattered.
Last year
In July of 2025, Australian labs found a new influenza A(H3N2) and named it subclade K. Its surface protein had changed. It did not match the vaccine.
The Australian season, normally twenty weeks, ran thirty-three. Australia counted nearly half a million confirmed cases, the most since records began in 1991, and 1,701 deaths, the worst of the century. Subclade K reached thirty-four countries. By late January the United States had recorded 280,000 hospitalizations and 12,000 deaths, nearly all from this one variant.
Timing caused the trouble. Subclade K appeared after the vaccine formula was set. A vaccine takes six months to make; a virus drifts in six weeks.
A second reason the vaccine underperformed deserves attention. The immune system remembers the first flu it ever met and keeps reaching for that memory — immune imprinting. When a drifted virus arrives, adults answer it with old antibodies that no longer fit. Children have less to unlearn, and it showed. The vaccine protected three children in four and one adult in three.
What Australia shows now
The southern season is nearly finished, and it reads better.
Cases have fallen: 29,300 by early May, half the count at the same date last year. The timing has returned to normal. If that pattern holds as the viruses move north, our peak should fall in the old place, December through February, rather than in early November as it did last year.
H3N2 still leads in both countries. A smaller H3N2 season is still an H3N2 season, and H3N2 is hard on the older population.
Two findings complicate the good news. In Australia, hospital admissions fell while intensive care admissions rose: fewer sick people, more very sick ones. And New Zealand is suffering its worst season for severe illness since 2021, not because of the virus but because vaccine was scarce and the people to give it were scarcer.
New Zealand teaches the lesson. The virus sets the ceiling. Coverage decides where beneath it you land.
New Mexico
Three high-severity seasons running would be new territory; the CDC has never recorded it. Two heavy H3N2 seasons have left immunity behind, and this year's vaccine has been rebuilt around subclade K. But the variant continues to evolve, and our exposure has less to do with the virus than with our own numbers.
The season here has not started. PopHIVE's dashboard shows the state at its late-summer floor. PopHIVE scales activity from 0 to 100 and smooths it over three weeks, which makes it a fine instrument for knowing when and a poor one for counting cases.
From the last complete season, the state recorded 1,916 flu hospitalizations. Adults 75 and over accounted for a third of them. Seventy-six adults and three children died of influenza.
1 in 3 of New Mexico's flu hospitalizations in 2024–25 were adults 75 and older — the group for whom the stronger vaccines have the best evidence, and the group a 23 percent coverage rate fails.
This year's vaccines
Every product is trivalent: H1N1, an updated H3N2, and B/Victoria. B/Yamagata has not appeared anywhere since March 2020 and has been dropped. Below 65, the CDC prefers no one shot over another.
Vaccine | Type | Ages | Notes |
Afluria, Fluarix, FluLaval, Fluzone | Egg-grown, standard dose | 6 mo+ | The “workhorses” |
Flucelvax | Cell-grown | 6 mo+ | Egg-free |
Flublok
| Recombinant protein | 9 yr+
| Egg-free; triple the antigen |
Fluzone High-Dose | Egg-grown, quadruple antigen | 65+ | Preferred at this age |
Fluad | Adjuvanted (includes an extra ingredient to boost its effectiveness) | 65+ | Preferred at this age |
FluMist | Live, nasal spray | 2-49 | Healthy, not pregnant; can be given at home |
mFLUSIVA | mRNA | 50+ | New |
Egg allergy no longer governs the choice or calls for watching afterward.
Eggs nudge the virus to adapt, moving it away from what circulates. H3N2 offends worst. Flucelvax and Flublok avoid eggs, which recommends them in a drift season where supply and cost permit. The evidence suggests this; it does not settle it.
mFLUSIVA prevents one additional case for every 125 people vaccinated, compared with a standard shot. The benefit is real and small. No one has tested it against the high-dose or adjuvanted vaccines, and its approval above 65 rests on antibody measurements rather than on patients who fell ill or did not. It hurts more, and insurers vary. For a patient of 70, high-dose or adjuvanted has better support. mFLUSIVA belongs between 50 and 64, where nothing else is preferred.
The nasal vaccine, at length
FluMist deserves its own discussion, because it is the only vaccine on the list that works by a different mechanism, and because its record is the most argued over.
Shot-delivered vaccines deliver killed virus to a muscle and the body answers with antibodies in the blood, chiefly IgG, which meet the virus after it has already established itself in the airway. As a nasal spray, FluMist delivers weakened live virus to the nose, where flu actually begins. The body answers there, with IgA on the mucous membrane, along with a cellular response — a fuller imitation of natural infection.
In theory the nasal route should win. In American practice it has not, consistently, and the reason remains unsettled.
In the 2012–13 and 2013–14 seasons the nasal vaccine performed poorly in American children. One network estimate put its effectiveness against any influenza at 3 percent, with a confidence interval running from below zero to 37, while the shot measured 63 percent in the same children. The ACIP withdrew its recommendation for two seasons. The manufacturer reformulated the H1N1 component, and the vaccine returned in 2018–19 and has been recommended since.
Meanwhile, the United Kingdom, which vaccinates schoolchildren by nose as national policy, kept measuring effectiveness near 60 percent, and as high as 80 percent against influenza B. Nobody has satisfactorily explained the gap. The leading suspicions: the weakened H1N1 strain replicated too feebly in the nose to teach anything; the three vaccine strains competed with one another inside the nose; or repeated prior vaccination, more common in American children, blunted the response. Possibly all three.
What recommends it
No needle. For a child who fights the shot, or an adult who avoids the clinic because of one, a vaccine given is worth more than a better vaccine refused.
Immunity where flu lands. Mucosal IgA plus a cellular response, closer to what natural infection produces.
Possibly broader. That wider response may hold up better against a drifted strain the vaccine was not built for — relevant in a subclade K world, though unproven.
May reduce spread. Blocking infection at the nose plausibly cuts onward transmission, which is the argument behind Britain's school program.
Strong British record. Around 60 percent effectiveness in children, up to 80 percent against influenza B.
Available at home. Sold direct to consumers again this year for self-administration — a real advantage for families far from a clinic.
Easy to schedule. Can be given with, before, or after other live vaccines, and does not interfere with a TB skin test.
What argues against it
An erratic American record. Two seasons of near-zero measured effectiveness, a two-year withdrawal, and no clear account of why the American and British data disagree.
Narrow age window. Ages 2 through 49 only. It is no help to the people flu hurts most.
Real contraindications. Not in pregnancy, not for the immunocompromised, and not for several chronic conditions. Ask before assuming.
It sheds. Vaccine virus persists in the nose for seven to ten days, more in small children. The virus is weakened and the risk is slight, but households containing a severely immunocompromised person are usually steered to the shot.
Antivirals disable it. Recent oseltamivir or baloxavir can inactivate the vaccine virus. Check timing before spraying.
It is egg-grown. Not a barrier for egg allergy any longer, but it does not escape the egg- adaptation problem that makes Flucelvax and Flublok attractive this year.
Different side effects, not fewer. A running or blocked nose, sore throat, and in small children sometimes fever.
How I would decide
For a healthy child between two and eight who dreads needles, the nasal spray is a good choice and often the difference between vaccinated and not. For a healthy adult under fifty with a genuine needle phobia, the same holds, with one honest caveat: in the United States the shot has the better effectiveness record, and the patient should hear that before choosing. For anyone pregnant, immunocompromised, chronically ill, or over fifty, it is not a candidate.
And in a season shaped by an H3N2 drift, I would not choose it for a patient who has another good option and no objection to a needle. The theoretical case for broader protection is attractive. It is not yet evidence.
How well vaccination works
In a well-matched year, the flu shot prevents half of medically attended illness. Last year, against subclade K, it did less.
Poor numbers, honestly reported. They describe how often vaccination prevented an infection, which is not the same question as how often it prevented a catastrophe.
85% of the children who died of flu last season had not been vaccinated. Preventing infection and preventing catastrophe are different jobs, and the vaccine does the second far better. Nearly every complaint of “I got the shot and got sick anyway” confuses them.
Side effects are brief: a sore arm, a headache, some aching, gone in a day or two. The high-dose and adjuvanted versions cause these more often and remain as safe.
Three rarer events deserve mention. Some people faint after a shot, which argues for seating them, not for skipping it. Children under five run a small excess of febrile seizures on the first day. And Guillain- Barré, if it once followed a flu shot within six weeks, calls for a considered conversation rather than a refusal.
When to go
September or October. After last November, September is the safer bet for anyone at real risk.
Miss the window? Get the shot anyway. A late shot beats none, and the virus will still be here.
Sources: New Mexico Department of Health; PopHIVE (Yale School of Public Health); CDC, ACIP, and VRBPAC; UNM Health Sciences Center; Eurosurveillance (Dapat et al., December 2025); Australian Centre for Disease Control; Australian Bureau of Statistics; Doherty Institute; Virology Down Under; interim MMWR effectiveness estimates for 2025–26; manufacturers' prescribing information. Season-shape chart is schematic, drawn from reported timing rather than plotted case counts. This article is general information and does not replace advice about an individual patient.
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