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.

There is no evidence that drinking in moderation is harmful after most vaccinations.

In general, there are several reasons to avoid excess alcohol consumption after a vaccination. Excess alcohol consumption can potentially mask the side effects of the vaccine and make it difficult to determine which side effects are attributable to the vaccine or alcohol.

Excessive alcohol consumption on a regular basis may also affect your immune system. Research has shown that alcohol intake of 15 or more drinks per week for men and 8 for women may suppress the immune system along with other factors such as smoking, a lack of sleep and a poor diet.

If you do decide to drink following a vaccine, you should attempt to drink in moderation. If you are concerned about this, you should contact the doctor or nurse administering the vaccine to confirm the safety of alcohol intake following an upcoming vaccine.

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 do I manage common vaccine side effects?

Many types of vaccines have similar mild side effects which can be managed at home. Common side effects include localised pain, swelling or redness at the injection site, fatigue, muscle or joint pain, weakness, mild fever, or chills.

These side effects indicate that your body is building immunity against the disease. To manage these side effects, over the counter painkillers and fever reducers such as paracetamol or ibuprofen can be taken.

Plenty of rest and hydration are recommended following a vaccine. Most side effects should last no longer than two days. If they last longer, contact your medical provider.

Serious reactions to vaccines occur extremely rarely. If you experience a life-threatening allergic reaction, such as swelling in the face, lips, tongue, throat, difficulties breathing or hives, get immediate emergency medical assistance.

What are the side effects of the flu vaccine?

Like any medical products or medicine, the flu vaccine can cause side effects. Common side effects include redness, warmth or swelling at the site of the injection, headaches, tiredness or body aches. Over the counter pain relievers such as ibuprofen or paracetamol can be used to reduce these symptoms.

Rarely, fainting or dizziness may be experienced. This can be relieved by resting during and after receiving the flu vaccine. A mild fever is also a rare side effect and can also be relieved by taking paracetamol or ibuprofen.

Side effects should not last any longer than two days. Contact the doctor or nurse who is administering the vaccine if you are concerned about post-flu shot side effects.

Importantly, as the flu vaccine is not a live vaccine it cannot give you the ‘flu’.

What are the side effects of the typhoid vaccine?

The typhoid vaccine is used to prevent typhoid fever, a serious potentially life-threatening illness caused by Salmonella Typhi bacteria. The vaccine is widely considered to be both safe and effective at preventing this illness. However, a range of side effects may be experienced following the vaccine.

Two types of typhoid vaccine are available: a live, attenuated (weakened) oral vaccine and an inactivated (killed) vaccine in the form of an injection.

Side effects for the injection typically include swelling, redness or pain at the injection spot, headache, fever and general discomfort. These side effects can be alleviated through rest, over the counter pain medications, and hydration.

Side effects for the oral typhoid vaccine may include mild loosening of the bowel motions, nausea,  and abdominal discomfort or cramping within 12-24 hours after each capsule is ingested. Very rarely people may have moderate diarrhoea or vomiting. Oral typhoid vaccine side effects can be minimised through hydration and rest. If these side effects become severe, contact a medical provider.

Side effects for both typhoid vaccines should not last for more than two days after receiving them. As with any vaccine or medication, there is a very small risk of developing a serious reaction. However, typhoid fever is far more dangerous to your health than the typhoid vaccine. If you have any questions about the typhoid vaccine, or its side effects, contact the medical provider who administered the vaccine to you.

Should I exercise after getting a vaccination?

Generally, it is safe to exercise after vaccinations. However, it may be prudent to avoid very strenuous exercise for a couple of hours after a vaccination. You may experience side effects that could inhibit your usual workout intensity such as local tenderness. If you develop other side effects such as fatigue or body aches in the several days after vaccination, this may also reduce your capacity to exercise. If this does occur, try a lighter exercise than usual, and make sure to listen to your body.

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