6–12 Month Vaccines
Japanese Encephalitis Vaccine Side Effects in Children
The JE vaccine usually causes only a sore arm, a mild fever and a little fussiness that settle within a day or two.
Written and fact-checked by the ParentVibes editorial team against WHO, IAP, CDC and NHS immunisation guidance. Not yet reviewed by a named clinician.
Quick facts
- Usually given
- 9 months & 16–18 months
- Where
- JE-endemic districts of India
- Protects against
- Japanese encephalitis (brain infection)
- Typical reaction
- Sore arm ± mild fever or fussiness
- Usually settles in
- 1–2 days
The Japanese encephalitis vaccine guards against a mosquito-borne virus that, though uncommon, can be devastating — it can inflame the brain and leave lasting damage in the small number of children it affects severely. In India, JE is given free under the National Immunization Schedule in districts where the disease is known to circulate, typically at 9 months and again at 16–18 months.
Parents in JE-endemic areas often ask why their child is offered a vaccine that friends in other cities don't get. The answer is geography: the virus is spread by mosquitoes that breed around paddy fields and livestock in particular regions, so the vaccine is targeted where the risk is genuine. Reassuringly, its side effects are usually mild and brief.
What the JE vaccine is
The Japanese encephalitis vaccine used in India's programme is given as an injection, usually into the thigh in babies or the upper arm in older children. It trains the immune system to recognise the JE virus so the body can fight it off after a mosquito bite.
JE is offered under the national programme only in endemic districts — parts of Uttar Pradesh, Bihar, Assam, West Bengal and several other states — because the virus circulates among mosquitoes, pigs and water birds in those areas. Where the risk is low, the vaccine isn't routinely given, which is why the schedule differs from place to place.
Vaccine, not the whole answer
The vaccine is the main protection, but reducing mosquito bites still helps — nets, covering clothing and clearing standing water lower the risk of JE and other mosquito-borne illnesses too.
Common JE vaccine side effects
Most children tolerate the JE vaccine well. When effects do appear, they are usually mild and show up soon after the shot:
Soreness at the injection site
The spot where the injection was given can be tender, red or slightly swollen for a day or so. It settles on its own without treatment.
Low-grade fever
A mild temperature in the first day or two is a common, expected sign that the immune system is responding to the vaccine.
Irritability or fussiness
Babies and toddlers are often a little more clingy, unsettled or hard to please on the day of the shot, easing by the next day.
Tiredness or reduced appetite
Some children are sleepier or feed a bit less than usual for a day. Rest and extra cuddles are all that's needed.
Headache in older children (occasionally)
Older children who can describe it may mention a mild headache for a short while. It typically passes within a day.
What's usually normal after the JE vaccine
These mild, short-lived reactions are all part of a healthy response:
- A tender, slightly red or swollen spot at the injection site.
- A mild fever in the first 24–48 hours.
- Being fussier, clingier or more unsettled than usual for a day.
- A little extra tiredness or a smaller appetite on the day of the shot.
- A brief, mild headache in an older child who can describe it.
- Your child otherwise drinking, playing and settling much as normal.
How long JE vaccine side effects last
- Soreness or redness at the injection site: usually 1–2 days.
- Low-grade fever: typically settles within a day or two.
- Irritability and fussiness: generally gone by the next day.
- Tiredness or reduced appetite: usually back to normal within a day.
- Any mild headache in an older child is short-lived and passes quickly.
Home care after the JE vaccine
Straightforward comfort measures cover almost everything:
Comfort & the injection site
- A cool, clean, damp cloth held gently on the site for a few minutes can ease soreness.
- Let your child move the arm or leg normally — gentle use helps the tenderness settle.
- Offer extra cuddles, comfort and calm play to an unsettled baby or toddler.
- Don't rub hard or put creams or home remedies on the injection spot.
Fever & fluids
- Offer plenty of fluids and dress your child in light, comfortable clothing.
- If your child is uncomfortable with fever, you can give paracetamol in the dose your doctor has advised for your child's weight; never give aspirin to a child.
- Keep the day gentle and allow extra rest if your child seems tired.
- Continue to protect your child from mosquito bites with nets and covering clothing.
Warning signs — see a doctor urgently
Serious reactions to the JE vaccine are rare, but seek urgent care for:
Seek urgent medical care if your child has
- Signs of a severe allergic reaction — difficulty breathing, swelling of the face, lips or tongue, or widespread hives (usually within minutes to an hour of the shot).
- A high fever with your child looking seriously unwell, or a fever in a baby under 3 months.
- A febrile seizure — a fit or convulsion during a fever.
- Unusual drowsiness, or your child being very hard to wake or unresponsive.
- Any new confusion, a severe or worsening headache, or a stiff neck — these deserve urgent care whatever the cause.
- Repeated vomiting, or a rash of small purple or red spots that don't fade when pressed.
Call your doctor immediately — or go straight to the nearest emergency department.
🩺 Find a paediatricianFor trouble breathing, facial swelling, a seizure lasting more than 5 minutes, or an unresponsive child, go straight to the nearest emergency department.
When to call your paediatrician
Not an emergency, but worth a call or a visit:
- Fever that lasts beyond about 48 hours or keeps climbing rather than settling.
- The injection site becomes increasingly red, hot, painful or swollen after a day or two.
- Your child stays unusually unsettled, sleepy or off their feeds beyond the first day.
- You're unsure whether your district's schedule means a second dose is due.
- Any symptom that worries you or seems more than the mild effects described here.
Frequently asked questions
Why is my child getting the JE vaccine when my relatives' children aren't?
Japanese encephalitis circulates only in certain regions, spread by mosquitoes that breed around paddy fields and livestock. The vaccine is offered free under the national programme in JE-endemic districts where the risk is real, so children in other areas may not be given it routinely. It's about local risk, not a difference in care.
Is the JE vaccine safe for my baby?
Yes. The vaccine used in India's programme has a good safety record, and most children have only mild, short-lived effects such as a sore arm, a mild fever or a day of fussiness. Serious reactions are rare, and the protection it gives against a potentially devastating brain infection is well worth it in endemic areas.
How many doses of the JE vaccine does my child need?
Under the national programme in endemic districts, JE is usually given as two doses — around 9 months and again at 16–18 months. Completing both doses gives the best protection. If you're unsure what your district's schedule advises, ask your vaccination centre or paediatrician.
My child has a fever after the JE shot — what can I give?
If your child is uncomfortable with fever, offer plenty of fluids and you can give paracetamol in the dose your doctor has advised for your child's weight. Never give aspirin to a child. A mild fever for a day or two is expected, but a high fever with your child looking unwell needs a check.
Does the JE vaccine mean I don't need to worry about mosquitoes?
The vaccine is your main protection against Japanese encephalitis, but preventing mosquito bites still matters — nets, covering clothing and clearing standing water lower the risk of JE and other mosquito-borne diseases like dengue and malaria that the vaccine doesn't cover.
Can the JE vaccine cause the brain infection it protects against?
No. The vaccine cannot give your child Japanese encephalitis. That said, any new confusion, a severe headache or a stiff neck after any illness deserves urgent medical care whatever the cause — so always get those symptoms checked promptly.
Your next steps
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The full IAP-style immunisation chart from birth to the teen years, explained in plain language.
See the full scheduleFind a paediatrician
Worried about a reaction, or due for the next dose? Find a trusted paediatrician near you.
Find a pediatricianRelated vaccine guides
Sources
- WHO — Vaccine safety and side effects
- Indian Academy of Pediatrics (IAP) — Immunization guidelines
- CDC — Possible side effects from vaccines
- NHS — NHS vaccinations and when to have them
- WHO — Japanese encephalitis vaccines position paper
- CDC — Japanese encephalitis vaccine
- MoHFW — National programme for Japanese encephalitis
Next review due: 6 January 2027.
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Medical disclaimer
This page is educational information about common vaccine reactions and is not a substitute for medical advice, diagnosis or treatment. Every child is different — always follow the guidance of your paediatrician or vaccination centre. If your child has trouble breathing, swelling of the face or throat, a fast heartbeat, hives all over, dizziness or weakness soon after a vaccine, or seems seriously unwell at any point, seek emergency medical care immediately. When in doubt, always get your child checked — it is never a waste of anyone's time.
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