The single most effective thing you can take to prevent the flu is the seasonal flu vaccine, which this season reduces your risk of a flu-related doctor visit by 24% to 36% and your risk of hospitalization by about 31%. Beyond vaccination, a combination of prescription antivirals, targeted supplements, and everyday habits can further lower your chances of getting sick.
The Flu Vaccine
All flu vaccines for the 2025–2026 season are trivalent, meaning they protect against three circulating strains: an A(H1N1) virus, an A(H3N2) virus, and a B/Victoria lineage virus. Anyone six months or older is eligible. The vaccine works better against some strains than others. This season, protection against influenza B ranges from 45% to 71% in children and up to 63% in adults, while protection against influenza A hovers closer to 34% to 38%.
If you’re 65 or older, a high-dose vaccine is worth asking about. It contains four times the antigen of a standard-dose shot, which helps older immune systems mount a stronger response. The result is better protection in the age group most vulnerable to serious flu complications.
Sleep Matters Around Vaccination
Getting enough sleep in the days surrounding your flu shot directly affects how well it works. In one study of healthy young adults, shorter sleep during just the two nights before vaccination led to significantly lower antibody levels that persisted for months. A separate randomized trial found that total sleep deprivation the night after getting vaccinated reduced antibody production by roughly 60% in male participants within the first five days. Aim for at least seven hours per night in the few days before and after your shot to get the most out of it.
Prescription Antivirals for Exposure
If someone in your household has the flu, a prescription antiviral can prevent you from catching it. One option approved for post-exposure prevention in people five and older works as a single, one-time dose taken within 48 hours of contact with an infected person. The dose is weight-based: 40 mg for most people, 80 mg if you weigh 80 kg (about 176 pounds) or more. Because it’s a single dose rather than a multi-day course, it’s one of the simplest preventive options available. Your doctor can determine whether you’re a good candidate, particularly if you’re at high risk for complications.
Vitamin D
Your vitamin D level plays a measurable role in how well your immune system fights respiratory infections. A large study of over 12,600 people found that those with vitamin D blood levels at or above 60 ng/mL had a 43% lower risk of flu-like illness compared to people with levels below 20 ng/mL. That’s a significant gap.
Levels below 12 ng/mL are considered deficient, 12 to 20 ng/mL inadequate, and above 20 ng/mL adequate. But “adequate” and “optimal for immune function” aren’t the same thing. Research shows that blood levels of at least 30 ng/mL are needed to trigger optimal production of cathelicidin, an antimicrobial protein your body uses as a first-line defense against viruses. If you live in a northern climate, spend most of your time indoors, or have darker skin, your levels are more likely to be low. A simple blood test can tell you where you stand, and supplementation through the winter months is a reasonable strategy if your levels are below 30 ng/mL.
Zinc Lozenges
Zinc has the strongest evidence for shortening colds once they start, but the mechanism (interfering with how viruses replicate in your throat and nasal passages) is relevant to flu prevention too. Clinical trials have used zinc acetate lozenges delivering 80 to 92 mg of elemental zinc per day, dissolved in the mouth every two to three hours while awake. Each lozenge contained roughly 9 to 13 mg of zinc.
It’s worth noting that these doses are well above the normal daily recommended intake and were used for short periods during active illness, not as a long-term supplement. High-dose zinc taken for more than a few days can cause nausea and may interfere with copper absorption. Keeping zinc lozenges on hand for the first sign of symptoms is a more practical approach than daily use throughout flu season.
What About Elderberry?
Elderberry extract is one of the most popular natural flu remedies, and earlier small studies suggested it could shorten flu symptoms by as much as four days. However, a more rigorous randomized, double-blind trial of 87 participants found no difference between elderberry and placebo. The elderberry group took an average of 5.3 days to reach mild symptoms, compared to 4.9 days for placebo. Complete resolution took 8.6 and 8.7 days, respectively. Neither difference was statistically meaningful. Based on the best available evidence, elderberry is unlikely to prevent or meaningfully shorten the flu.
Everyday Habits That Reduce Transmission
The flu virus spreads through respiratory droplets and contaminated surfaces, so physical barriers matter. Washing your hands with soap and water remains the gold standard. When that’s not available, hand sanitizer with at least 60% alcohol effectively kills influenza viruses, though concentrations between 60% and 95% perform best.
Indoor humidity also plays a surprising role. The flu virus survives longest in dry air. On surfaces, it breaks down much faster at higher humidity levels. At 75% relative humidity, virus levels on stainless steel surfaces dropped to undetectable within 15 minutes in lab conditions. At 20% relative humidity (typical of heated winter air), the virus persists far longer. Running a humidifier to keep indoor humidity between 40% and 60% creates a less hospitable environment for the virus while staying comfortable for you.
Putting It All Together
No single measure is foolproof, but stacking several strategies creates meaningful protection. Get your flu shot (and sleep well around it). Keep your vitamin D levels above 30 ng/mL through the winter. Wash your hands frequently or use alcohol-based sanitizer. Humidify your indoor air during cold months. Have zinc lozenges ready if you start feeling off. And if a household member gets the flu, ask about a one-dose prescription antiviral within 48 hours of exposure. Each layer adds protection, and together they significantly reduce your odds of spending a week in bed.