The safety profile of Comirnaty™ is like that of other vaccines given in New Zealand. Some people experience mild to moderate discomfort at the injection-site and flu-like symptoms (such as headache, muscle and joint aches, fever) for just a day or two after vaccination. These are more commonly reported after the second dose and in younger adults. This is an expected response not experienced by everyone.

Who should this vaccine not be given to?

  • Anyone with severe allergy (anaphylaxis) to a previous dose of this vaccine or a component of the vaccine.
  • Administration of Comirnaty™ should be postponed in individuals with an acute febrile illness (fever over 38°C) or who are systemically unwell. The presence of a minor infection is not a reason to delay immunisation.
  • Defer vaccination if myocarditis or pericarditis occurs following a previous dose of COVID-19 or another vaccine. Seek advice from IMAC medical advisors.

Potential responses to Comirnaty

The most common reactions and adverse events after vaccination include, headache, fatigue, muscle aches, nausea and generalised ‘flu-like symptoms.

  • These are the expected responses and were seen in the clinical trials. 
  • Not everyone experiences these responses – they will still be protected by the vaccine.
  • These reactions occur more commonly after the second dose lasting for a day or two.
  • They are more common in people under 50 years
  • Some people (around 1 in 5 people) feel unable to do their normal activities or work the day after vaccination. 
  • Other adverse events reported following vaccination can be associated with stress or anxiety responses to being injected – dizziness, fainting, rapid heartbeat.

Severe allergic reactions (anaphylaxis) can occur almost immediately after any vaccination. (see Immunisation Handbook, chapter 2)

How do risks of contracting COVID-19 disease compare with getting a vaccination?

Risks from COVID-19

Potential responses to mRNA COVID-19 vaccine (Comirnaty)

Two-thirds of unvaccinated people infected with the SARS-CoV-2 virus will have COVID-19 symptoms. It can take up to 2-5 days (up to 14) days after infection for symptoms to begin.

Infected people are infectious for around 2 days before symptoms start.

Commonly reported symptoms include:

  • new or worsening cough
  • sneezing or runny nose
  • fever
  • sore throat
  • Loss of smell or taste
  • shortness of breath

Other symptoms, that almost always occur with ones above, include :

  • diarrhoea
  • sore muscles
  • headache
  • nausea/vomiting
  • malaise
  • chest pain
  • abdominal pain
  • joint pain
  • confusion.

Common (1 in 4–10 people): usually lasting 1–2 days after vaccination and more common after dose 2:

  • tiredness and lethargy
  • pain at the injection site
  • headache, nausea, dizziness, flu-like illness
  • muscle aches and joint pain
  • chills and fever.

Uncommon (1 in 100 to 1 in 1000 people):

  • swollen lymph nodes
  • insomnia
  • itching at injection site

As with any medicine, very rarely, severe allergic reactions occur following immunisation (approximately 5–7 cases per 1 million doses)

Myocarditis and pericarditis (inflammation of the heart) can occur rarely (approx 1 in 25,000 young men aged <30 years). Four times lower risk than after COVID-19.



Of those, some will have severe disease and need support to breathe in hospital.

The risk of severe disease increases in people who have underlying health conditions, such as diabetes, heart disease, lung disease, high blood pressure, or are pregnant.


Complications include:

  • severe breathing difficulties needing ventilator support
  • infection of the heart and heart failure
  • blood clotting disorders.


Around 7-10 cases in 1,000 may die.


The likelihood of dying from COVID-19 increases with age. Ranging from:

    • 1 in 10,000 at age 25
    • 4 in 1,000 at age 55
    • 15 in 1,000 at age 65
    • 1 in 20 at age 75
    • 3 in 20 at age 85


COVID-19 can be a serious illness in young adults – of those who need hospital treatment many may require intensive care.


Long-term complications of the heart, lung and nervous systems have been associated with COVID-19 (Long-COVID).


Last updated: 29 March 2023