Your Biggest Flu Shot Questions, Answered

As a family physician, I’ve been encouraging my patients to get their annual flu shot for years. And although the recommendation from doctors like me may be straightforward, there’s still a lot of lingering skepticism around vaccines, especially post-COVID. But here’s the truth: The flu is still very much around, and it can be serious—even fatal.

So, let’s talk about what the flu vaccine does, who really needs it (hint: basically everyone), and clear up any doubts you might have. Because rolling up your sleeve can help keep you, your family, and your community safe.

How the flu vaccine works

The flu shot relies on either an inactivated virus or a protein-based technology that helps your immune system fight off the virus.

• Inactivated (killed) virus prevents the flu virus from replicating in your body.
• Recombinant or protein-based tech are specific viral proteins that spur your immune system into gear.

There is also a nasal spray, which is a live vaccine that we only give to younger, healthy individuals.

It takes about two weeks for those antibodies to fully ramp up, so if you get exposed to the flu right before or right after your shot, you can still get sick. That’s why some folks mistakenly believe, “The flu shot gave me the flu!” That’s just bad timing during flu season. Rest assured, the vaccine itself isn’t a live virus.

I often get asked about thimerosal, a mercury-based preservative. Single-dose flu shots typically don’t contain thimerosal at all. If you’re curious or concerned, ask for the vaccine package insert or talk to your health care provider—most will happily share those details.

Along those same lines, some patients are concerned that there’s a link between the flu vaccine and fertility issues or birth defects. Let me be clear: There’s no evidence linking the flu shot to either. I understand the concerns, but social media myths don’t stand up to real data.

Flu vaccine benefits

Some folks assume the flu shot is only about preventing the infection altogether, but it’s also about reducing the severity of your illness should you contract the flu virus. If you do end up in the ER or ICU with flu complications like pneumonia or severe respiratory issues, your outcome tends to be better if you’ve been vaccinated. Here’s what data consistently shows when it comes to the benefits of vaccination:

• It lowers your risk of flu-related doctor visits and hospitalizations.
• It reduces your likelihood of flu-related death.
• It often lessens the intensity (and duration) of symptoms if you do get sick.
• Some research even suggests a reduced risk of heart attacks triggered by the flu.

No vaccine is 100% perfect, but I believe that even partial protection beats the alternative.

Who really needs the flu shot?

The answer: pretty much everyone over 6 months old. But if you or someone you love is in a higher-risk category—like older adults, pregnant people, those with chronic conditions (like asthma or diabetes) or those who are immunocompromised—then I consider it nonnegotiable. Flu complications such as pneumonia or hospitalization are far more likely if your immune system is already taxed.

And if you’ve got an infant under 6 months old at home (who can’t yet receive the shot), everyone in the household should get vaccinated. It helps create a protective “cocoon” around your baby until they’re old enough for their own shot. If you have a child under 9 who’s never had a flu vaccine before, they will need two doses.

Of course, there are a few exceptions—infants under 6 months and anyone who has had a severe allergic reaction to the flu vaccine or its components shouldn’t get the shot. If you’re unsure, talk with your clinician.

Why the flu vaccine changes each year

Flu viruses mutate—a process we call antigenic drift—so public health experts track global trends to predict which strains will take center stage. Scientists need to formulate the vaccine months before flu season hits, so there’s a bit of a forecasting element at play.

The exact effectiveness varies each year, hinging on how well the chosen strains of the vaccine match the ones actually circulating. Factors like your age and health status can also affect how strongly your immune system responds. And sometimes the virus morphs unexpectedly, leading to what we call a “mismatch.”

Still, even an imperfect match offers protection against severe symptoms and reduces your chances of complications. From a public health angle, vaccines are our top strategy for minimizing hospitalizations and preventing widespread flu surges.

Which flu vaccine is right for you?

Modern medicine provides patients with a number of vaccine options, including:

Inactivated flu vaccine: The standard shot for those 6 months and older.

High-dose vaccine: Contains more antigen for people 65+ who might need the extra immune boost.

Egg-free formulations: Ideal if you have a severe egg allergy or prefer a non-egg-based version.

Nasal spray: This is the only live vaccine and is given to younger, healthy individuals, ages 2 to 49. Availability can vary.

If you’re pregnant, immunocompromised, or have a chronic condition, check in with your health care provider to find the best fit.

Flu shot FAQ: Your top questions, answered

Q: Can the vaccine actually give me the flu?
A: No, it can’t. As mentioned, the flu shot uses inactivated or non-replicating components. The nasal spray is a “live attenuated” vaccine, but it’s specifically engineered so it won’t cause full-blown illness.

Q: What if I have a compromised immune system?
A: If you’re immunocompromised, it’s even more important to shield yourself with a flu shot.

Q: Is it safe to combine flu and COVID shots?
A: Yes, and current research shows no dip in effectiveness if you receive them at the same time. (If you’re 60+ or have certain health conditions, ask your doc about RSV vaccination, too.)

Q: I’m pregnant—should I wait?
A: No. Getting vaccinated while pregnant helps protect both you and your baby. Plus, the immune benefits can pass to your little one for those crucial first six months.

Q: Is it ever too late in the season to get the flu shot?
A: Definitely not. Flu can linger into the spring, and a late-in-the-game shot is better than no shot at all and can help you avoid a bad case. In my own practice, I usually offer flu shots until mid-April.

Q: How long does flu vaccine protection last?
A: Typically, your flu shot keeps you covered for the rest of that flu season (about six months). Over time, those antibodies fade, which is why the CDC urges everyone to renew their shot each fall.

Q: I read the flu shot is made with eggs and I’m allergic. Can I still get the shot?
A: There are egg-free and preservative-free vaccines available, so be sure to speak to your health care provider about it.

Q: Isn’t natural immunity better?
A: The flu can be dangerous, especially for vulnerable individuals. While you do build immunity after having the flu, it’s not worth the risk of severe complications—or passing it to someone more at risk, like a newborn or an older family member.

Q: Where can I get the shot?
A: Your primary care doctor should have the flu shot. You can also get it at local pharmacies and clinics, which typically offer walk-in options or easy appointments.

Q: Will my insurance cover the flu shot?
A: Most plans cover it, so cost is rarely a barrier.

No matter how hectic life gets, don’t underestimate the power of a quick vaccine to protect you—and everyone around you—from serious illness. The flu might seem like no biggie but trust me: Once you’ve seen how bad it can get, you’ll understand why health pros like me keep urging you to get the shot every year.