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What to Expect From This Year’s Flu Season
Last year’s flu season hit older adults especially hard. Here’s what experts are watching this year — and how to protect yourself
5-minute read
Kyle Hilton
It’s not your imagination: Last year’s flu season really was brutal — among the worst in decades. The culprit? A wily, fast-spreading, mutated version of the H3N2 virus, nicknamed “subclade K,” that emerged only months after the season’s flu vaccine had already been formulated.
That mismatch meant the vaccine was less effective than usual, reducing the risk of flu-related hospitalization by roughly 30 percent in adults, compared with the 40 to 60 percent effectiveness seen in a typical, well-matched season.
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Older adults were especially hard hit. People 65 and older were hospitalized with the flu at more than double the rate of any other age group, and it wasn’t a coincidence. More than 9 in 10 flu cases were caused by subclade K, which has historically affected older adults the most.
Although it’s hard to fully predict the outcome of this year’s flu season, infectious disease experts are optimistic based on a few clues, most notably what they have glimpsed in Australia and other southern hemisphere countries, where winter (and flu season) has already come and gone.
“Predictions are hard to make, given that we don’t fully understand all the variables, but we often look to the southern hemisphere influenza season in the months immediately preceding ours as a predictor,” says Dr. Michael Ben-Aderet, medical director of hospital epidemiology at Huntington Health, a Cedars-Sinai affiliate, and associate director of hospital epidemiology at Cedars-Sinai Medical Center. “This year, that flu season was unusually mild in both the number of cases and the average severity of disease. So we are hopeful that our flu season will be similar.”
Another good omen: “It’s rare to have bad flu seasons back-to-back,” says Dr. Scott Roberts, assistant professor of infectious diseases at Yale School of Medicine. “Generally, if there is a bad flu season, it will lead to spikes in immunity against that flu strain, which will often have some protective immunity into the next flu season.”
Will this year’s flu shot be a good match?
Influenza viruses change constantly, which allows them to sneak past your immune system’s defenses. That’s why flu vaccines are updated most years. For instance, in response to the subclade K strain that caused so much misery last winter, all three components of this year’s flu shot have been updated so that the vaccine specifically targets the new variant.
This season also brings something new to the flu-fighting arsenal: The first flu vaccine to use mRNA technology — called mFlusiva — was recently approved by the U.S. Food and Drug Administration for adults 50 and older.
In a large clinical trial of about 41,000 adults, mFlusiva was about 27 percent more effective than a standard-dose flu shot at preventing the flu — a relative comparison between the two vaccines, not a measure of how much flu it prevents overall. The results were similar for people 65 and older. But the study didn’t compare the effectiveness of the new vaccine to the high-dose flu shot, which is commonly recommended for older adults, notes Roberts, “so it remains to be seen how well it will compare for those groups.”
“My general advice is that the best flu vaccine option is the one you are going to get,” he adds. “Any flu vaccine is better than no flu vaccine.”
But there’s another advantage to mRNA vaccines: They can be made in about six weeks, compared with roughly six months for traditional flu shots. That means a vaccine could be updated later in the year if an unexpected strain starts spreading — something that wasn’t possible with last year’s mismatched vaccine.
Which flu vaccine — and when?
For most adults ages 50 to 64, any age-appropriate flu vaccine — standard-dose, high-dose, adjuvanted, recombinant, cell-based or the new mRNA option — offers protection, and the U.S. Centers for Disease Control and Prevention doesn’t recommend one over another for this age group.
That’s not the case, however, if you’re 65 or older. For this population, the CDC recommends any of the following three options: Fluzone (high-dose), Fluad (adjuvanted) or Flublok (recombinant). If none of these are available when you go in for your shot, don’t wait — get whichever age-appropriate flu vaccine is on hand. Experts say delaying vaccination to hold out for a specific brand isn’t worth the risk.
“The reason older adults get sicker with influenza, including more complications and hospitalizations, is primarily due to slowing down of the immune system as we age, a normal process that impacts all adults,” says Ben-Aderet. “Because of this, it takes older adults longer to clear the virus and increases the risk of complications. In addition, the complications of severe illness, like fever, elevated heart rate and blood pressure changes, are likely to affect older adults more profoundly.”
That’s especially true if you have a chronic health condition, like heart disease, lung disease (such as COPD or asthma), diabetes, kidney disease, or a weakened immune system from illness or medication. Talk with your doctor about timing and which vaccine option makes sense for you.
Don’t wait if you get sick
No flu vaccine is perfect. And while this year’s shot is expected to meaningfully lower your risk of getting sick with the flu, research, including a recently published review of studies published in JAMA, shows that even in years with reduced effectiveness, vaccination still lowers your risk of severe flu if you do get sick.
Watch for fever or chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches and fatigue — all symptoms of the flu — and see your health care provider at the first sign of symptoms rather than trying to power through to see if they improve on their own.
The go-to treatments — antiviral medications like oseltamivir phosphate (Tamiflu) and baloxavir marboxil (Xofluxa) — work best when started within 48 hours of symptom onset, says Roberts. Wait even a few days and you’ll miss that window.
“Also, if we know someone has the flu, the at-risk exposures, such as close contact family members, can receive [a type of preventive treatment] to reduce the odds of becoming sick,” he adds. “I see this missed even among clinicians, and it’s especially important around the holidays, which is when multigenerational households get together at peak flu season.”
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