How Well Does the Flu Shot Really Work? What New Research Shows

What did researchers look at?

A team of researchers reviewed 69 separate studies on flu vaccines, published between August 2025 and June 2026, to answer two questions: How well do flu shots actually protect people? And are they safe? This wasn’t one study — it was a pooled look at dozens of studies covering different ages, health conditions, and vaccine types, including the most recent 2025–2026 flu season.

The stakes are real. During just the most recent season (October 2025 through February 2026), the CDC estimated at least 340,000 flu-related hospitalizations and 21,000 flu-related deaths in the U.S.

How well does the flu shot protect adults?

For adults 65 and older, getting a flu shot cut the risk of being hospitalized with flu by about 31% during the 2025–2026 season. That number moved around from year to year — as low as 19% in one recent season and as high as 43% in another — because how well the vaccine matches that year’s circulating flu strains changes every season. Vaccination also lowered the risk of dying from flu among older adults, by 29% up to as much as 66%, depending on the season and vaccine type studied.

For adults 19 to 64, a flu shot cut the risk of flu hospitalization by about 29% in the 2025–2026 season, and lowered the risk of lab-confirmed flu illness by roughly 24% to 36%, depending on which national data source researchers used.

No flu shot is 100% effective, and that percentage shifts by season. But across every season and every study the researchers reviewed, the same pattern held: vaccinated adults were hospitalized and died from flu less often than unvaccinated adults.

Does it help protect children and pregnant people?

Yes. Among children and teens (6 months to 17 years), flu vaccination was linked to an 80% lower risk of dying from a lab-confirmed flu infection, based on 8 seasons of national data. For children with underlying health conditions that raise their risk from flu, vaccination lowered the risk of flu hospitalization or ER visits by 48%, and lowered the risk of death by 77%.

A flu shot during pregnancy also protects the baby after birth. Infants whose mothers were vaccinated during pregnancy had a 44% lower risk of a lab-confirmed flu infection during their first 6 months of life — before they’re even old enough to get their own flu shot. In the same body of research, a flu shot during pregnancy was not linked to a higher risk of a baby being born small for its gestational age, and was actually linked to a lower risk of preterm birth.

Should adults 65 and older ask about the high-dose shot?

It may be worth a conversation. A large clinical trial in Denmark followed more than 330,000 people over 3 flu seasons and found that a high-dose flu vaccine was about 44% more effective at preventing flu-related hospitalization than the standard-dose flu shot in adults 65 and older. If you’re in this age group, ask your doctor whether the high-dose version is available and right for you.

Is the flu shot safe?

The safety data here is reassuring. One study tracked nearly 10 million people who received a flu vaccine and found no increased risk of serious problems like Guillain-Barré syndrome (a rare nerve condition), stroke, anaphylaxis, or swelling of the brain or spinal cord — whether the flu shot was given alone or alongside a COVID-19 or RSV vaccine.

A separate study focused on young children (6 months to 5 years) found no increased risk of febrile seizures (seizures brought on by fever) in the week after vaccination. And, as noted above, a study of tens of thousands of pregnant people who got a flu shot found no increased risk to the baby.

Across everything this review covered, the researchers identified no new safety concerns.

What should you do next?

Every study has limits. The researchers noted that only a small share of the studies they reviewed were rated as very high quality, and a vaccine effectiveness number from one season doesn’t automatically carry over to the next, since circulating flu strains change every year. Still, the overall pattern — fewer hospitalizations and deaths among vaccinated people, and no new safety red flags — held up across nearly every age group studied.

If you’re weighing whether a flu shot is worth it this year — especially if you’re 65 or older, pregnant, or caring for a child with a chronic health condition — MHP’s primary care team sees patients of every age, from infants to seniors, and can talk through your options, including whether a higher-dose flu vaccine makes sense for you. Reach out to schedule a visit before flu season ramps up.

Source: Senerth E, Sheikholeslamian SM, Sivakumaran K, et al. “Influenza Vaccine Effectiveness and Safety for the 2026-2027 Respiratory Season.” JAMA. Published online September 2, 2026. doi:10.1001/jama.2026.18126

This article is for general information and is not medical advice. Please talk with your doctor about what is right for you.