On This Page

Flu Shot for Babies

Flu season is here again… and it’s time to think about protecting yourself and your babies, toddlers, and big kids! Here are some fast flu facts and tips for how to stay healthy throughout flu season...

Fast Flu Facts

First things first…what is the flu?

The flu is a viral infection that mostly affects the breathing passages (from the nose to the lungs) and can even affect the brain and entire body. If you’re suffering from the flu, you’ll have a fever (100 to 103 degrees Fahrenheit), cough, sore throat, headache, muscle aches, and extreme fatigue. No fun, right? Unlike the common cold, the flu (also known as influenza) can knock you out for one to two weeks…and by weakening your immune system for many weeks…long after the flu is over! It commonly leads to serious secondary infections, like sinusitis or pneumonia.

The flu is especially hard on vulnerable populations.

Kids younger than 5 years old are vulnerable because their immune systems are still immature. And, seniors over 65 often have frail immunity, too...which can push them into serious secondary illnesses. In fact, seniors are two to three times more likely to suffer a heart attack in the month after the flu. Influenza killed an estimated 21,000 people in the US during the 2022-2023 flu season, including 116 children…and nearly 12,000 kids were hospitalized. On the flip side, the CDC estimates that the flu shot prevented 65,000 hospitalizations and 3,700 deaths. 

How does the flu spread?

Influenza is highly contagious (especially a few days before you come down with symptoms and for the entire time you have fever). It is spread two ways: 1) by touch (a sick person touches their nose or mouth and then deposits the germs by touching a door knob, restaurant menu or elevator button and 2) through tiny droplets from sneezing, coughing, or talking.

These points underscore why doctors believe flu shots are so important!

What to Know About the Flu Shot for Babies

Flu shots are recommended for kids 6 months or older, according to the American Academy of Pediatrics. Babies and toddlers getting the flu shot for the first time need two doses with four weeks in between. If your child has an egg allergy, it’s still safe for them to receive the vaccine.

Why do kids need two flu shots?

Babies under 2 and children who have never received the flu shot before need two doses of the flu shot—administered about four weeks apart—because they are less likely to have come in contact with the virus. The first shot primes their little immune systems, while the second helps them develop flu-fighting antibodies.

How long does it take for a child’s body to be immune to the flu after getting the flu shot?

It takes up to two weeks for the body to become immune to the flu after the second shot. Remember, if your child needs two shots but has only gotten a single shot, it will not protect them from the flu.

What are the side effects of the flu shot for infants?

Possible side effects of the flu shot for babies include:

  • Soreness or redness in the area of the flu shot

  • Swelling in the area of the shot

  • Headaches

  • Mild fever

  • Nausea

  • Muscle aches

Do flu shots for babies and toddlers contain mercury?

Ask for a shot from a single-dose, mercury-free vial. Multi-dose vials contain a mercury-based preservative to kill bacteria introduced by repeated needle penetrations into the vial. With a single dose vial, mercury isn’t necessary.

Pregnant women should also receive the flu shot (from a single-dose vial). The shot does not contain live viruses, so it’s safe for the fetus inside.

It can be hard watching your little one get pricked by a needle. Once your child is over 2 years old, you can choose to give the vaccine as an injection or as a nasal spray. (See more tips for calming your tot's shot fears!)

When is the best time to give baby the flu shot?

Ideally, it’s best to get vaccinated by Halloween, but you can still get it through February...late is better than never!

Can you get the flu shot with your COVID vaccine? 

Yes—the CDC says that it's completely save to receive your flu and COVID vaccines at the same time. 

Final Thoughts on Flu Shots for Babies

Unfortunately, influenza is a pretty sneaky infection. You can still catch it even after getting the vaccine, but the illness will likely be less intense than if you didn’t get the shot. And, by getting the shot, you’ll be helping protect your friends and neighbors—especially those struggling with serious illnesses—by doing your part to build to your community’s “herd immunity.”

Related stories: 

About Dr. Harvey Karp

Dr. Harvey Karp, one of America’s most trusted pediatricians, is the founder of Happiest Baby and the inventor of the groundbreaking SNOO Smart Sleeper. After years of treating patients in Los Angeles, Dr. Karp vaulted to global prominence with the release of the bestselling Happiest Baby on the Block and Happiest Toddler on the Block. His celebrated books and videos have since become standard pediatric practice, translated into more than 20 languages and have helped millions of parents. Dr. Karp’s landmark methods, including the 5 S’s for soothing babies, guide parents to understand and nurture their children and relieve stressful issues, like new-parent exhaustion, infant crying, and toddler tantrums.

View more posts tagged, health & safety

Have questions about a Happiest Baby product? Our consultants would be happy to help! Submit your questions here.

Disclaimer: The information on our site is NOT medical advice for any specific person or condition. It is only meant as general information. If you have any medical questions and concerns about your child or yourself, please contact your health provider.