By Dr. Richard Rupp and Bridget Hawkins

Dear VaccineSmarts,

Last year, I got the flu shot and ended up getting sick. What gives?

Horatio from Dickinson

Dear Horatio,

We sometimes hear this from parents coming in for their children’s immunizations.

While we have sympathy for those who become ill after receiving their flu shot, we can assure you that the flu shot does not give you the flu.

That being said, there are a few reasons why people might be experiencing illness following their flu shot. They might have been sick before receiving the flu shot or they might be sick from a cold virus that has similar symptoms to the flu.

Sometimes people end up getting the flu despite receiving the flu shot and experience more mild symptoms (the vaccine is not 100 percent effective), or they might have contracted a strain of the flu that is not covered by that year’s flu shot.

Every year, the flu vaccine makers determine which strains of the flu virus will be circulating in the United States. Sometimes their predictions are incorrect and alternate strains spread instead, rendering that season’s flu vaccine ineffective for those particular strains.

But improvements in technology and methods used to predict the strains have made this less likely in recent years. New vaccines are being developed that target a part of the flu virus that is common in all of the known strains of the flu virus.

If they are safe and effective, it’s thought that these universal vaccines would replace the seasonal flu vaccines, reducing the amount of flu vaccines needed throughout a person’s lifetime.

Flu shots are recommended for anyone older than 6 months, but are especially important for people who have a higher risk of complications from the flu such as pregnant women, those with chronic illnesses or compromised immune systems and senior citizens.

If you fall into one of these groups, you should consult your physician before obtaining a flu vaccination.

Another option for families to consider is “cocooning,” which is when all of the family members get vaccinated to protect a vulnerable family member in the house — such as a grandparent or a child with leukemia — from being exposed to the flu.

Even if you are the type of person who never gets sick, you should think about getting immunized to protect not only you, but your loved ones as well.

Dr. Richard Rupp is a pediatrician and member of UTMB's Sealy Center for Vaccine Development. Dr. Bridget Hawkins, Ph.D., is the assistant director of the Sealy Center for Vaccine Development. This column is supported by a UTMB President's Cabinet Award to provide information about vaccines. Visit for more information.