Japanese encephalitis (Ixiaro) vaccine side effects explained: how common they are, how long they last, who should take care, and when to seek help. Advice from our Chislehurst pharmacists.
The Japanese encephalitis vaccine has a well-established safety record, and for most people any side effects are mild and brief. If you are weighing the vaccine up, knowing what to expect makes the decision easier. This page sets out the common reactions, the rare ones, and who should take extra care. For the schedule, doses and who needs the vaccine in the first place, see our complete guide to the Japanese encephalitis vaccine.
In the clinical studies of Ixiaro, the Japanese encephalitis vaccine used in the UK, the most frequently reported reactions were mild and predictable. The figures give a useful sense of how likely each one is.
Less commonly, some people notice a mild fever, nausea, a flu-like feeling or a short-lived skin rash. In children, irritability and reduced appetite are sometimes reported. These reactions are a normal sign of the immune system responding, and they pass quickly.
Most reactions need nothing more than a little patience. Keep the vaccinated arm moving to ease stiffness, stay well hydrated, and rest if you feel tired. Paracetamol or ibuprofen manages soreness, headache or a mild temperature well for most people, unless you have been advised not to take them. If something is worrying you in the days afterwards, you are always welcome to call us.
A serious allergic reaction to any vaccine is possible but very rare. For this reason we ask you to wait a short while at the pharmacy after your jab, and both our pharmacies are equipped to manage a reaction should one occur. Ixiaro contains protamine sulfate, which can cause sensitivity in a small number of people, so we always check your allergy history first. After you leave, seek urgent medical help and call 999 if you develop difficulty breathing, swelling of the face or throat, or feel faint.
A few groups need a tailored conversation before the vaccine. In pregnancy the vaccine is generally avoided and given only when the risk of infection clearly outweighs the risk of vaccination. If you have a bleeding disorder, an injection into the muscle may not be suitable and an alternative route can be considered. If you are unwell with a feverish illness on the day, we usually wait until you have recovered. Telling us about your medical history and any medicines you take lets us give the vaccine safely, which is part of every consultation. The full Japanese encephalitis vaccine guide covers the schedule and dosing that sit alongside this.
Injection-site soreness in about 1 in 3 people, headache in about 1 in 5, and muscle aches and tiredness in about 1 in 8. They are usually mild and settle within a day or two.
Most reactions clear within 24 to 48 hours. Arm soreness can linger a little longer but is rarely troublesome.
No, they are very rare. As a precaution you wait a short time after vaccination, and our pharmacies are equipped to manage a reaction in the unlikely event one happens.
Yes. Paracetamol or ibuprofen manages most soreness, headache or mild fever well, unless you have been told otherwise.
It is generally avoided in pregnancy and given only if the risk of infection clearly outweighs the risk of vaccination. Talk it through with us and your midwife before booking.
Yes. Ixiaro contains protamine sulfate, so tell us about any previous vaccine reactions or known allergies. We check this before vaccinating.
Reassured but still deciding? Read the background in our detailed Japanese encephalitis vaccine information, then book a short consultation and we will answer anything else in person.
Ready to take the next step?
Book your consultation at either Chislehurst Pharmacy Group location. Same-day and next-day appointments usually available.
