Seeing your child unsettled or feverish after a vaccination visit is common, and it can still be worrying even when you know it's expected. This article explains what a normal reaction looks like, what genuinely needs medical attention, and why the small chance of a mild reaction is not a reason to delay vaccination — see our guide on timely vaccination for why sticking to the schedule matters.
Why some reaction is actually expected
A vaccine works by prompting your child's immune system to respond and build protection. Some children develop a mild, short-lived reaction as part of this process, but this isn't a reliable sign either way — many children build full protection with little or no noticeable reaction at all, so the absence of a reaction doesn't mean a vaccine "didn't work." This also doesn't mean every reaction is harmless by default, which is why it's worth knowing what's typical and what isn't.
Common, expected reactions
- At the injection site: pain, redness, or mild swelling, usually settling within a couple of days
- Fever can occur after vaccination and usually settles within a short period on its own — the exact timing and how long it lasts vary by vaccine, so ask your pediatrician what to expect for the specific vaccines your child is receiving
- Fussiness, irritability, or being more unsettled than usual
- Reduced appetite or extra sleepiness
These are genuinely common and don't need treatment beyond comfort measures in most children.
What you can do for comfort
- A cool, clean compress over the injection site can ease local pain or swelling
- Continue breastfeeding or your child's usual feeds as normal — there's no need to withhold feeds after vaccination
- For fever or discomfort, use paracetamol or ibuprofen only as advised by your pediatrician for your child's weight and age — a low-grade fever on its own doesn't automatically need medicine
- Extra cuddling and a calm environment help more than most parents expect
The 30-minute wait after vaccination
Your doctor may ask you to stay at the clinic for about 30 minutes after vaccination. This period is specifically for observing your child for any immediate reaction, such as a severe allergic reaction — it's a standard precaution, not a sign that something is expected to go wrong.
Uncommon but important reactions
Most children never experience these, but it's worth knowing what to watch for. Contact your doctor promptly if your child has:
- A high fever after vaccination
- Continuous, inconsolable crying lasting more than 3 hours
- Becomes unusually limp or unresponsive — this is rare
- A convulsion (seizure)
Signs of a severe allergic reaction — seek emergency care
A severe allergic reaction (anaphylaxis) to a vaccine is rare, but it's serious enough to know the signs. It typically appears within minutes of the injection, which is exactly why the 30-minute observation period matters. Seek emergency care immediately if your child develops:
- Widespread hives or swelling, especially of the face, lips, tongue, or throat
- Difficulty breathing or breathing that sounds different
- Sudden paleness, floppiness, or looking seriously unwell
A special note on fever in very young infants
Babies receive several vaccine doses before 3 months of age. Regardless of a recent vaccination, a measured temperature of 38.0°C (100.4°F) or higher in a baby under 3 months old always needs immediate medical assessment — see our Signs Your Newborn Needs Urgent Medical Attention guide. At this age, a fever can't be safely assumed to be "just" a vaccine reaction, since the same picture can also indicate a serious infection that needs prompt evaluation.
Common misconceptions worth addressing
- "Vaccines cause autism." This has been extensively studied and there is no scientific evidence supporting this claim.
- "Oral polio drops cause impotence." There is no scientific evidence for this either — it remains a persistent but unfounded rumour in some communities.
- "Giving several vaccines at once overwhelms a child's immune system." A child's immune system handles an enormous number of antigens every day through ordinary exposure to the environment; the number of antigens in the recommended schedule is a very small fraction of that capacity.
None of this means vaccines carry zero risk — no medical intervention does — but the well-documented risk of the diseases vaccines prevent is far greater than the risk of the vaccines themselves.
Frequently asked questions
Should I give paracetamol before vaccination to prevent a reaction? This isn't generally recommended as a routine practice. A mild, low-grade fever after vaccination doesn't need treatment on its own, and treating pre-emptively isn't standard advice — ask your pediatrician if you have specific concerns.
My child had a strong reaction to the first dose — will later doses be worse? Not necessarily. Reactions vary between doses and don't reliably predict what will happen next time. Mention any reaction you noticed at your next visit so your doctor has the full picture.
We fell behind on the vaccination schedule — does a reaction mean we should stop? No — a typical mild reaction isn't a reason to stop or delay future vaccines. If your child has already missed one or more doses for any reason, see our guide on catch-up vaccination for how to safely get back on schedule.
Is it true that vaccines are completely risk-free? No, and it isn't accurate to claim that. Like any medical intervention, vaccines carry a small risk of reactions, most of them mild. What the evidence consistently shows is that this risk is far smaller than the risk of the diseases being prevented.
See our Child Vaccination service page for more on how vaccination is approached at this clinic.
Further reading
- Recommendations for Vaccination — IAP Guidelines for Parents
- About Vaccines for Your Children — CDC
- Vaccine Safety — CDC
General, current guidance for educational purposes — not individualized medical advice. Always discuss your child's specific vaccination questions or reactions with your own pediatrician.