Q: Can a flu shot cause a fever and vomiting in my child, and should we visit the clinic?
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 child received a flu vaccine yesterday morning and developed a fever of 38.2°C (100.8°F) by the evening. I gave a fever reducer, and the fever went down overnight, but it came back this morning at 38.1°C (100.6°F). I gave another dose of the fever reducer followed by some milk, but about two hours later, my child threw up. The temperature is currently down to 37.5°C (99.5°F). Could the fever and vomiting be related to the flu shot? Do I need to take my child to the doctor?
Answer:
It can be very concerning when a child develops a fever and begins vomiting after receiving a vaccination.
Current Assessment
Developing a mild fever (around 38°C / 100.4°F) and experiencing a single episode of vomiting within 24 hours of receiving the flu vaccine can be expected post-vaccination reactions. The fact that your child’s temperature has dropped to 37.5°C (99.5°F) is an encouraging sign.
What You Can Do at Home
Provide small, frequent sips of fluid: Wait about 30 to 60 minutes after the vomiting episode before offering liquids. Then, offer 1 to 2 teaspoons of water or an oral rehydration solution every 5 to 10 minutes. Giving too much fluid at once may trigger the vomiting reflex again.
Hold off on milk and heavy foods: Temporarily avoid dairy, milk, and greasy foods, as these can irritate a sensitive stomach.
Keep them comfortable: Dress your child in light, breathable clothing and keep the room at a comfortable temperature.
Use fever reducers thoughtfully: Fever reducers (such as acetaminophen or ibuprofen, depending on age) are primarily used to relieve discomfort. You can give them if your child is irritable or in distress, or if the fever rises above 38.5°C (101.3°F).
Vaccine Reaction vs. Other Illnesses
Mild fever, nausea, or mild vomiting within 24 to 48 hours are known side effects of the immune response to a vaccine. However, an unrelated illness—such as viral gastroenteritis (stomach flu)—can also occasionally coincide with the timing of a vaccination.
When to Seek Immediate Medical Evaluation
Contact your pediatrician or visit a local clinic right away if you observe any of the following warning signs:
Signs of dehydration: No urination or wet diapers for more than 4 hours, dry lips, a dry mouth, or crying without tears.
Persistent vomiting: Repeated vomiting or an inability to keep any fluids down.
High or prolonged fever: A temperature of 39°C (102.2°F) or higher, or any fever persisting beyond 48 hours.
Altered alertness: Extreme lethargy, difficulty waking, lack of eye contact, or unusual irritability.
Other red flags: Labored or rapid breathing, a stiff neck, or complaints of severe abdominal pain.
For now, focus on slow, gentle hydration. If any of the warning signs above develop, or if symptoms do not improve after 48 hours, please consult a healthcare professional for an in-person assessment.
For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.
