Q: My 42-month-old has a high fever of 40.1°C after a flu shot and antipyretics aren't working. Should we go to the ER?

Medically reviewed by Sang Hyun Ahn, MD

Content edited by Myeongchan Kim, MD

This post is a dramatization of a question and answer session experienced by our actual medical reviewers. Please note that this content is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.

Question:

My 42-month-old daughter (93 cm, 13 kg) received her flu vaccination at 3:00 PM yesterday. Starting at 4:00 AM today, she has been experiencing a continuous high fever ranging from 39°C to 40.5°C. I have been alternating fever reducers and applied a cooling patch, but her temperature is not dropping. Her current temperature is 40.1°C. I gave her 4.5 ml of dexibuprofen, and when the fever didn't go down, I gave her 5 ml of acetaminophen two hours later. Should we take her to the emergency room?

Answer:

Yes, you should go to the emergency room immediately.

If a high fever of 39°C to 40.5°C persists after a vaccination and does not respond well to cross-dosing fever reducers, it is critical to rule out the possibility of an underlying infection rather than just a simple vaccine reaction. While mild fevers are very common within 24 to 48 hours after receiving a vaccine, a fever this high and stubborn requires proper medical investigation to find the exact cause.

What to do on your way to the hospital:

• Offer her small sips of fluids (water or pediatric electrolyte drinks) every 5 minutes to prevent dehydration.

• Hold her in an upright sitting position.

• Write down and bring a memo detailing the exact names, dosages, and times of the medications you have given her so far.

What to expect at the emergency room:

• Blood and urine tests to check for any bacterial or viral infections.

• An assessment of her hydration and electrolyte levels.

• Professional fever-reducing treatments or antibiotics, if the doctor determines they are necessary.

Please head to the nearest emergency department right away so your child can be evaluated safely.

For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.

fevercoach.us

Apple App Store

Google Play

🌐 Also available in: Español · 한국어