Is It Still Working? The Truth About Mid-Season Flu Shot Protection

Flu season can last from early fall all the way through late spring in Alberta, and it often peaks between December and February. If you got your flu shot back in October, it’s natural to wonder whether your protection is starting to fade.

The short answer? Flu shot protection does decrease over time, but you’re still much better protected than if you hadn’t gotten it at all. Understanding what the vaccine does, and doesn’t do, is the key to navigating this stage of the season. 
 

What You Need to Know About Flu Shot Duration and Effectiveness

1. Immunity Starts ~2 Weeks After the Shot 

Your body needs time to develop antibodies. After you get the flu shot, it takes about two weeks to reach full protection. That’s why early fall vaccination is recommended.

2. Protection Lasts Several Months 

While exact timelines vary, most studies suggest peak protection lasts about 3 to 4 months. So, if you got vaccinated in October, you likely still have good protection through January, though it may start to wane afterward.

3. You’re Still Protected From Severe Illness 

Even if your flu shot becomes less effective at preventing infection, it still helps reduce the severity of symptoms if you do catch the flu. That means lower risk of hospitalization and fewer complications.

4. Flu Strains Can Evolve Mid-Season 

Sometimes, new strains of the virus emerge during the season that weren’t part of the original vaccine formula. This doesn’t make the shot useless; it still provides partial protection and can help reduce spread and severity.

5. You Likely Don’t Need a Booster 

In most cases, a second flu shot isn’t needed in a single season unless you’re a child receiving your first flu shot or have a unique medical condition. If you’re unsure, a pharmacist at UPharmacy can assess your situation and provide guidance.
 

What To Do If You’re Still Getting Sick

Some people get sick after their flu shot and wonder if it “didn’t work.” Here’s what to keep in mind:

• It might not be the flu – Other viruses like RSV, colds, or COVID-19 can mimic flu symptoms.
• You may have had exposure before full immunity developed – If you got sick within 1–2 weeks of your shot, your immune system may not have been ready yet.
• Mild symptoms aren’t a failure – If you get the flu and recover quickly, your vaccine helped reduce severity.

If you’re feeling sick now, don’t panic. UPharmacy can assess your symptoms and provide flu treatment options, including antiviral prescriptions where appropriate. 
 

Still Have Questions? UPharmacy Can Help

Mid-season is a great time to check in on your health and immunity. Whether you’re unsure about your flu shot, feeling under the weather, or just want to stay ahead of illness, UPharmacy’s pharmacists are here to support you.

We offer walk-in consultations, symptom assessments, and trusted advice to help you make informed decisions during cold and flu season. With locations in Calgary and Edmonton, it’s easy to get the help you need.

If you’re wondering whether your flu shot is still effective, contact UPharmacy today.