Q: My child has a fever after getting the flu vaccine. Is it a vaccine reaction or an upcoming cold?
Updated: Sep 7
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:
Hello doctor. My child got the flu vaccine yesterday around 10:00 AM. A mild fever (37.7°C) started in the afternoon, reaching 38.6°C around 1:00 AM. After taking a fever reducer once, the fever went down and stayed normal until this afternoon, when a mild fever (37.6°C) started again. It is currently at 38.0°C.
Is this a continuous fever from the vaccination, or could it be a cold? For context, the pediatrician mentioned beforehand that there might be a slight onset of bronchitis, but since there was no fever and my child's overall condition was good, we were told it was safe to proceed with the vaccination.
Answer:
It is completely understandable that you are worried about the recurring fever after yesterday's vaccination.
Current Situation:
Having a mild fever (up to 38°C) within 24 to 48 hours after receiving a flu vaccine is a very common reaction. However, since your child already had early signs of bronchitis before the vaccination, it is highly possible that a normal vaccine reaction and the early symptoms of a respiratory illness are overlapping.
What You Can Do at Home:
Offer frequent, small sips of water or electrolyte drinks to maintain hydration.
Dress your child in light clothing and keep the room at a comfortable temperature.
Administer a fever reducer if your child is uncomfortable (be sure to check the correct dosage and time intervals).
Ensure they get plenty of rest.
Warning Signs to Watch For:
If you notice any of the following, please contact or visit your pediatrician today:
Difficulty breathing (e.g., skin pulling in under the ribs, or wheezing).
Extreme lethargy, poor oral intake, or no urine output for more than 8 hours.
Fever that lasts beyond 48 hours or spikes to 39°C or higher.
A sudden worsening of their cough or a change in the color of their phlegm.
Distinguishing Between a Vaccine Reaction and a Cold:
Vaccine Reaction: Usually starts within 24 hours of the injection and improves within 48 hours.
Overlapping Cold/Bronchitis: Respiratory symptoms like a runny nose or cough will progressively worsen, or the fever will persist for more than 3 days.
Please observe your child closely for one more day. However, if any of the warning signs mentioned above appear, or if you remain uncertain about their condition, be sure to contact your pediatrician for an in-person evaluation.
For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.
