Q: My 4-month-old baby has a fever after vaccinations. Should I give more medication or go to the ER?

Medically reviewed by Sang Hyun Ahn, 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. My baby is 4 months old (135 days) and weighs 7.1 kg. They received their 4-month vaccinations yesterday. Since last night, their temperature has been fluctuating, repeatedly rising above 38°C. I have given them a fever reducer three times at 4-hour intervals, but the fever is starting to rise again as the medication wears off. Should I give another dose of the fever reducer and continue to monitor them, or should I stop the medication and take them to the emergency room? Please advise!

Answer:

Hello! You must be very worried about your baby's fever following their 4-month vaccinations.

A fever of 38°C or higher is a common reaction after vaccinations and usually improves within 24 to 48 hours. For a 7.1 kg baby, here is the appropriate guidance:

【Fever Reducer Dosage Guide】

• Tylenol (Acetaminophen) dosage: 71-106 mg = 2.2-3.3 ml

• Recommended dosage: 2.8 ml (90 mg)

• Can be given every 4-6 hours, up to a maximum of 5 times a day.

• Since you have administered it 3 times so far, you can safely give up to 2 more doses today.

【Please check the following now】

→ Is the baby feeding well?

→ Is the baby urinating as usual?

→ Aside from the fever, is the baby excessively fussy or lethargic?

【When to visit the Emergency Room】

• Fever persists above 39.5°C

• Feeding volume decreases to less than half of their usual amount

• No urine output for more than 8 hours

• Baby is extremely fussy or completely limp/lethargic

• The injection site becomes severely swollen and red

Since vaccination-induced fevers mostly improve within 48 hours, if the severe symptoms mentioned above are not present, you may administer one more dose of the fever reducer and continue to observe your baby. Ensuring adequate hydration and dressing the baby in light clothing will also help.

If the fever of 38°C or higher persists into tomorrow, or if any concerning symptoms develop, please visit a pediatrician for an examination!

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

https://fevercoach.us