Why Did I Get the Flu if I Had the Vaccine?

Andrea Alemanni

Andrea Cudd Alemanni is an independent patient advocate and chemist, and owner of Patient Navigation Team. Contact her at 336-485-5427 or andrea@patientnavteam.com.

Did you get the flu this season, even though you were vaccinated?

As of February 9, the CDC estimated 7.2–8.4 million people sought medical treatment due to flu-like symptoms.

First, understand that getting an annual flu shot is strongly recommended and your healthcare professional can determine a best choice for you. Virus strains can be different each year, explaining the need for annual vaccination.

How the Flu Vaccine Makes a Difference
Your immune system is the key to protecting you from many diseases—influenza is no different.

When flu virus enters the body of an unvaccinated person, the immune system produces antibodies to fight the invader. However, this person’s body has never “seen” the flu. It will take several days for their immune system to build enough white blood cells to fight Influenza. Meanwhile, the virus multiplies and flu symptoms begin.

Contrast this with a vaccinated person exposed to flu. Because virus in the vaccine is weakened or inactivated, you develop protective antibodies without getting sick. Now your body can fight the invading virus with a ready arsenal. Your chances of contracting “full-blown” flu are drastically reduced.

And the (Short) Answer is…
Antibodies are like puzzle pieces, needing to fit onto the invading virus to properly do their job. If there’s an exact match, your chances of getting the flu are significantly reduced. If the white cells only partially fit to or recognize the virus, you may still get sick. In this case, symptoms and length of illness will be much less compared with an unvaccinated person.

What About Other Vaccines?
Other scheduled childhood vaccinations and immunizations work in a similar way. By introducing a very small amount of treated virus, the body builds immunity to the more dangerous version.

Modern vaccinations have nearly eliminated many dangerous and debilitating diseases, including polio. Members of Rotary International campaign to “End Polio Now” and travel hundreds of miles to distribute vaccinations to at-risk populations. Meanwhile, we are now seeing populations of children without vaccines experiencing “outbreaks” of both measles and chicken pox in the U.S.

Any risk in receiving vaccines is minimal and rare when compared to the effects of full exposure without protection. Talk to your healthcare professional about the best vaccine choices for you.