Reactions to vaccines

Vaccines are both effective and safe, however side effects sometimes occur. These are usually mild reactions and are part of the normal immune response to vaccination. Serious reactions to vaccination such as anaphylaxis are extremely rare.

Common mild vaccine reactions

Mild reactions can affect up to 15% of people following vaccination. These reactions generally occur within a day or two of immunisation and are transient. Live viral vaccines (MMR, Yellow Fever, Varicella) can occasionally cause symptoms such as fever, headache, tiredness and/or rash. These may be delayed until several days after vaccination.

Uncommon, severe adverse reactions

Although they can be severe, most rare vaccine reactions occur soon after immunisation, are self-limiting and do not lead to long-term problems. Anaphylaxis, for example, although potentially life-threatening, is quickly and very effectively treated and has no long-term effects. After vaccination, it is very important to stay for 10-15 minutes of observation.

If you have any concerns about the safety or effectiveness of vaccines, please feel free to discuss this with one of our doctors.

What are the likely side effects?

Modern vaccines are less likely to cause side effects, and there are no restrictions on normal activities - most people can work, drive a car, play sport or go to the gym. Still, it is better to take it easy if you are experiencing any side effects. Modern vaccines do not leave a scar.


If you have a history of fainting after injections, make sure you tell the doctor. You may be asked to lie down during vaccination and for a while afterwards so we can be sure you are feeling well before leaving the clinic.

What if I have a cold?

It is medically-safe to be vaccinated if you have a runny nose, sore throat or cough. You should delay vaccination if you have a fever over 39°C or are sick enough to have to stay in bed.

Allergic reactions (Anaphylaxis)

Allergic reactions are rare but may be very serious. After vaccination, notify one of our staff immediately if you feel:

  • Warm or itchy, or develop a rash
  • Faint (especially on standing up) or dizzy
  • Shortness of breath, or start to wheeze or cough
  • Your throat, face, hands or limbs begin to swell
  • Nausea or stomach pain
  • Suddenly tired

Symptoms usually develop within 15 minutes of vaccination, (hence the need to wait in the clinic after vaccination). Occasionally allergic symptoms can occur several days later. If you develop one or more of the above symptoms after leaving the clinic, seek medical help immediately. Persons with severe allergies to eggs may not be able to be immunised against yellow fever, flu, and MMR. Travellers with penicillin allergy however can be vaccinated safely.

Fevers and feeling unwell

Live virus vaccines such as Yellow fever, varicella (chickenpox) and MMR (measles, mumps, and rubella) may cause a fever, headache, tiredness and muscle aches in up to 15% of people, beginning 3-10 days after vaccination. MMR may also cause a transient rash in 5% of people. Most vaccines used today contain killed organisms or fragments of organisms and cannot cause the illness they are used to prevent. A good example is the flu vaccine which cannot cause the flu. However, some people react more strongly to vaccines and may feel unwell afterwards. If you develop a fever or become unwell after vaccination, please call our clinic and speak to one of our doctors or nurses.

Sore or red arm

The most common side effect following vaccination is a sore arm. If you use your arm normally after vaccination, it will help ease the soreness more quickly. In some people, vaccines may cause a lump or hardness at the injection site which persists for a few weeks. If your arm is red, hot and/or sore, place an ice pack over the affected area. You can take paracetamol. Intradermal vaccines (e.g. rabies) may cause itchiness at the injection site and a small surface lump which may persist for a few weeks. This is all part of a normal immune response to vaccination.

Can I drink alcohol after vaccines?

If taking typhoid capsules, alcohol (and food) must not be taken within a few hours of each capsule. However, it is OK to have alcohol after other vaccinations.

Diarrhoea or stomach problems

The oral typhoid vaccine (capsules) may cause mild to moderate nausea, stomach cramps and diarrhoea within 12-24 hours after taking each capsule. If symptoms are more severe after the second capsule, please call our clinic and speak to one of our doctors or nurses.

Will vaccines weaken my immune system?

There is no evidence that vaccination weakens the immune system. In fact, vaccination is a very effective way of strengthening the immune system’s response to diseases. However, to avoid the risk of unnecessary side effects, vaccinations should only be recommended when there is a significant risk of disease.

How long do vaccinations last?

The list below outlines the usual duration of protection once the vaccination course is complete. For some vaccines, the duration of protection is uncertain.

  • Chickenpox – long-term
  • Cholera (oral) - up to 2 years
  • Diphtheria - 10 years
  • Flu vaccine - up to 1 year
  • Hepatitis A - Probable lifetime protection
  • Hepatitis B - Lifetime
  • Japanese B Encephalitis - 2 years to , depending on the vaccine used
  • Measles, Mumps, Rubella - Life time
  • Meningitis - new conjugate vaccines give up to 5 years protection
  • Pneumonia - >5 years, probably life time
  • Polio booster - Life time
  • Rabies (pre exposure) - Immune memory persists for life; booster doses needed only
  • Tetanus - 5-10 years
  • Typhoid (injection) - up to 3 years
  • Typhoid capsules x 3 - 3 years
  • Typhoid capsules x 4 - 5 years
  • Whooping cough – immunity begins to wane after 3-5 years
  • Yellow Fever - Long-term; certificate valid for life