If the Flu Shot Is Meant to Protect Me, Why Am I Still Falling Sick?
Each flu season brings back the familiar symptoms—fever, body aches, sore throat, and fatigue. Doctors strongly recommend annual flu shots, yet many patients are puzzled when they still catch the flu after vaccination. This raises a common concern: If the flu shot protects us, why do some people still get sick?
The Flu Virus Keeps Changing
Influenza is unlike many other viruses—it mutates frequently. Each year, scientists predict the strains most likely to spread and design vaccines accordingly. If the virus changes after the vaccine is made, the protection may not be perfect. Even then, the vaccine usually provides partial defence and reduces the severity of illness.
Different People, Different Responses
Immune response to the vaccine varies. Healthy adults tend to build stronger protection, while older adults, children, or those with chronic diseases may have weaker responses. Still, for these vulnerable groups, even partial protection can prevent severe illness or hospitalisation.
Timing Matters
The flu shot needs about two weeks to become effective. If exposure happens too soon, illness may still occur. Protection can also fade slightly toward the end of a long flu season if vaccination is taken very early.
Not Every Illness Is the Flu
Other viruses—like RSV, rhinoviruses, and coronaviruses—cause flu-like symptoms. Sometimes people assume the flu shot “failed,” when in fact, they never had influenza to begin with.
Vaccines Make the Flu Less Dangerous
Even if you catch the flu, the vaccine usually makes it milder and less risky. Research shows that vaccinated people are less likely to suffer severe complications, need hospitalisation, or die from flu-related causes.
Conclusion
Think of the flu vaccine as a safety net—it may not block every fall, but it cushions the impact. For children, the elderly, and those with chronic illnesses, this can be life-saving. That’s why experts continue to recommend yearly flu shots as the best defence against influenza.