How are the COVID-19 risks calculated?
We have used trusted data sources (such as government reports and published scientific studies) to create a Bayesian Network model. A Bayesian network is a mathematical model that shows the relationship between factors and how they influence the chance of something happening. Examples of the CoRiCal model are here for Astrazeneca vaccine, here for the Pfizer vaccine, and here for long COVID. The data sources used and assumptions are listed here for Astrazeneca vaccine, here for the Pfizer vaccine, and here for the Paediatric Pfizer vaccine.

Why don’t all the CoRiCal models include health conditions that affect COVID-19 outcomes? (e.g. obesity, diabetes, cardiovascular disease, immunosuppression etc.)
Currently, only the long COVID risk calculator can take these factors into account. This is because of limited data for the other calculators. However, we are working on a new model for the Pfizer COVID-19 vaccine that will take health conditions into account.

Which COVID-19 variant is the calculator based on?
The current calculator assumes that 100% of COVID-19 cases are caused by the Omicron variant. We may update this in future.

How does having had COVID-19 previously and vaccination affect the outcomes?
The long COVID risk calculator includes how many times you’ve had COVID-19. COVID-19 can induce an immune response. This may give some short-term protection from getting COVID-19 again. But it may also increase your chance of getting long COVID. For the Pfizer COVID-19 vaccine, we are collecting new data on this and will update CoRiCal once we have enough evidence.

Are the rates given per whole population, or for the relevant age group population?
The rates are displayed as the number per 1 million people in the selected age and sex group. You can also display the results as a “1 in x” chance for the selected age and sex group.

Why is the risk of dying different between the risk charts and the interactive calculator?
This is because the interactive calculator is the latest update and assumes 100% of cases are caused by the Omicron variant. The risk charts were designed in January 2022, when it was assumed that 10% of cases were Delta and 90% were Omicron.

Is the calculator based on Australian data?
We have used Australian data sources where possible. Where Australian data are not available, we have used overseas data. All data sources are shown here (see Pfizer data sources , AstraZeneca data sources , and long COVID data sources).

What are the assumptions in the CoRiCal model?
Unfortunately there is not always data available to fit every situation. For example, if data are not available for specific age groups, we have to assume the chance is the same for a wide age group (e.g. 18-60 years). For a full explanation of the assumptions for each calculator, please follow the links in the MORE INFO tab.

What are the most common side-effects of the COVID-19 vaccines?
Pain around the injection site is the most frequently reported local side effect, most often the day after injection. According to a study of more than 600,000 people in the UK, local side effects were reported by:

• 71·9% of people after the first dose of the Pfizer COVID-19 vaccine
• 68·5% after the second dose of Pfizer COVID-19 vaccine
• 58·7% after the first dose of AstraZeneca COVID-19 vaccine

Does the calculator get any funding from pharmaceutical companies?
This calculator receives funding from the Immunisation Coalition, who in turn receives untied educational grants from pharmaceutical companies that manufacture vaccines. However, the CoRiCal project has not received any direct funding from AstraZeneca, Moderna, Pfizer, or any other companies that produce COVID-19 vaccines.

Does the calculator get any funding from governments?
No, the calculator is not funded by any governments. Nearly all the contributors (including both clinicians and academics) work on the calculator in their free time. A few people are doing the behind-the scenes programming of the Bayesian model. We update the models behind the interactive online tool when substantial new data are available, to make it easier for people to use the models.

Is the calculator designed to push vaccination?

No. The CoRiCal calculator is designed as a shared decision-making tool to help people weigh up the pros and cons of COVID-19 vaccines. It has been developed to simplify complex information about rare outcomes from COVID-19 and vaccines.

The calculator has been developed by researchers and clinicians who are not employed by the Immunisation Coalition, or vaccine manufacturers. The authors have not received any specific instructions from these organisations about the content.

The risk estimates that have been used are transparent and listed on the website that hosts the CoRiCal tool. The estimates change when the evidence changes. As stated above, the main purpose of the calculator is to help people discuss and make informed decisions about COVID-19 vaccines. You may want to discuss this information further with your vaccine provider (e.g. GP, pharmacist or nurse).

Where can I get more information about the CoRiCal tool?
If you would like to get some information or offer feedback, please complete the form via this link . You will need to include your email address if you would like someone to respond.

What is myocarditis?

Myocarditis is inflammation of the heart muscle. Pericarditis is inflammation of the lining around the heart. They can occur separately or at the same time.

There are many possible causes of myocarditis and pericarditis. COVID-19 can cause myocarditis and/or pericarditis in some people. Myocarditis and pericarditis are also rare complications after some COVID-19 vaccines, e.g., mRNA COVID vaccines made by Moderna or Pfizer.

Myocarditis and pericarditis are more likely in young males aged 15-40 years, and after the second dose of an mRNA COVID vaccine.

Myocarditis after COVID-19 is different and often more severe than myocarditis after a vaccine. Most people with myocarditis after a vaccine make a full recovery.

The risk of myocarditis and pericarditis are much lower in children aged 5 to 11 years compared to adolescents. The risk is also lower after a booster than the initial injections. Symptoms of myocarditis or pericarditis typically appear within 1 to 5 days of vaccination.

Common symptoms of myocarditis include:

• chest pain
• pressure or discomfort in the chest
• irregular, skipped heartbeats or ‘fluttering’
• fainting
• shortness of breath
• pain when breathing

If you are concerned about myocarditis and have any of the above symptoms, you should see a health professional.

To help parents make informed decisions, we developed a child version of the CoRiCal tool. Children with weak immune systems should consider a COVID vaccine booster every 12 months, for ages 5 to 17 (ATAGI advice, 2024). A COVID vaccine booster is not recommended for any children under the age of 5 years.

This frequently asked questions (FAQ) webpage outlines some of the questions that parents have asked about the COVID-19 vaccines. This includes side effects and how likely the COVID-19 vaccine is to prevent serious illness.

The information is consistent with ATAGI and the National Centre for Immunisation Research and Surveillance (NCIRS).

Are children at risk of getting COVID-19?
Yes. Everyone is at risk of getting COVID-19. Studies show that children and adolescents can play a role in spreading the SARS-CoV-2 virus. This is the virus that causes COVID-19. Spread between young children is just as common as spread between adults. The Omicron variants of COVID-19 are easier to spread. They cause more cases in children, but do not cause more severe disease. Children are most likely to catch COVID-19 from unvaccinated adults (household or close family) and at school. Children tend to get mild disease, and most do not need to go to hospital. Rarely, around 1 in 3000 children infected with COVID-19 develop a post-COVID inflammatory syndrome that affects many organs in their body. This is called paediatric inflammatory multisystem syndrome temporarily associated with SARS-CoV-2 (PIMS-TS). It is also called multisystem inflammatory syndrome in children (MIS-C).

Which children are most at risk from getting COVID-19?
Some conditions increase the risk of children needing to go to hospital with COVID-19. This includes:

• diabetes
• congenital heart disease
• chronic pulmonary disease
• neurological diseases
• being born premature
• being overweight

Should children get the COVID-19 vaccine?

While COVID-19 is mild in most children, a few can become very sick and have long term effects. Children are more likely to become very sick from COVID-19 if they have certain conditions (see list above). The COVID-19 vaccine reduces the chance that a child will get very sick from COVID-19. There is also some evidence that the vaccine reduces the chance of children getting multi-inflammatory syndrome after they catch COVID-19. Children can spread COVID-19 to others, especially members of their family and household. Vaccinated people are less likely to pass on the virus than unvaccinated people. The 2024 ATAGI advice on COVID vaccination boosters is shown below (Table 1).

What are the side effects of the COVID-19 vaccine?

Side effects are not common, but the COVID-19 vaccine can cause local injection-site pain, redness and swelling, headaches or general aches and pains. These side effects usually go away quickly. More severe reactions are very uncommon. A very small number of children get myocarditis (inflammation of the heart muscle) after the COVID-19 vaccine. This is more likely to happen after catching COVID-19 (see above). Myocarditis after getting COVID-19 is more severe than myocarditis after a COVID-19 vaccine.

Do the COVID-19 vaccines reduce the risk of myocarditis and going to hospital?
The chance of getting myocarditis and going to hospital is higher in unvaccinated children who catch COVID-19. The best protection is provided by having at least two doses of a COVID-19 vaccine. The vaccine also reduces the risk of multi-inflammatory syndrome after catching COVID-19.

Why does the kids model only look at the Pfizer vaccine?

In Australia, the Pfizer COVID-19 vaccine is approved and available for children aged over 5 years. The Moderna COVID-19 vaccine is registered and available for children ≥ 12 years. This is based on 2024 ATAGI advice. See their website for the most up-to-date information.

Novavax XBB.1.5 vaccine was not available when this model was developed. The original Novavax vaccine can be given to people aged 12 years and older, but ATAGI suggests that XBB.1.5-based vaccines are preferred. See their website for more information.

The long COVID version of CoRiCal aims to help people understand their chance of feeling unwell six months after getting COVID-19 (long COVID).

What is long COVID and who does it affect?

Long COVID is also known as post-COVID-19 condition or post-acute sequelae (consequences) of COVID-19. Long COVID means feeling unwell a long time after the infection (12 weeks or more). This can include continued, returning or new symptoms, that are not due to any other diagnosis.

These symptoms can impact everyday life and make it difficult to complete tasks, exercise, or work. While many people get better over time, some still have symptoms two years later or more. For this calculator, we show the chance of having long COVID 6 months after infection. Long COVID can happen after infection with any SARS-CoV-2 strain, but this calculator focuses on the Omicron variant.

What sort of symptoms can long COVID cause?
Long COVID can cause over 200 symptoms/conditions across many different organ systems in the body. This calculator focuses on the most common symptoms, listed below.

• Cardiovascular symptoms include:
  • abnormal heart rhythm (too fast, too slow, or irregular)
  • acute coronary (heart vessel) disease (heart attack)
  • atrial fibrillation (irregular heart beat)
  • chest pain
  • heart failure
  • hypertension (high blood pressure)
  • myocarditis (inflammation of heart muscle)
  • pericarditis (inflammation of tissue around the heart)
• Breathing symptoms include:
• cough
• interstitial lung disease (a number of lung diseases that cause scarring (fibrosis) of the lungs. The scarring causes stiffness in the lungs which makes it difficult to breathe and get oxygen to the bloodstream)
• low blood oxygen
• pleurisy (inflammation of the lung lining) or pleural effusion (when fluid builds up in the space between the lung and the chest wall)
• shortness of breath
• Metabolic symptoms include:
• diabetes mellitus (high blood sugar)
• hyperlipidaemia (high levels of fat in the blood, including cholesterol)
• needing insulin
• obesity
• Neurological symptoms include:
• bleeding in blood vessels that supply the brain (this can cause a stroke)
• 'brain fog' (confusion, difficulty thinking, slower response time)
• headache
• memory problems
• seizure
• smell and taste problems
• stroke
• Stomach and bowel symptoms include:
• constipation
• diarrhoea
• gastroesophageal reflux disease (reflux)
• oesophageal disorders
• liver disease

What other symptoms can there be?
Other symptoms from long COVID are listed below. These are not currently included in the calculator. We may add them at a later stage when more data is available.

• Blood conditions include:
  • anaemia (not enough healthy red blood cells)
  • deep vein thrombosis (blood clot in a deep vein, most often in the leg)
  • pulmonary embolism (blood clot in the lung)
  • superficial venous thrombosis (blood clot in a surface vein, most often in the leg)
  • thromboembolism (blood clot in a vein)
• Fatigue (feeling very tired all the time)
• Kidney conditions include:
• acute (short-term) kidney injury
• chronic (long-term) kidney disease
• Mental health conditions include:
• adjustment disorder
• anxiety
• depression
• mood disorder
• panic, stress, and trauma related disorders
• sleep disorder
• substance use disorders
• Musculoskeletal symptoms include:
• joint pain
• muscle pain
• muscle weakness
• Skin symptoms include:
• hair loss
• skin rash

Who is most at risk of getting long COVID?
Anyone can get long COVID, even if they had no symptoms during their first week of infection. You are more likely to get long COVID if you:

• are female
• have a high number of medical conditions
• have a severe case of COVID-19
• have not received COVID-19 vaccines
• do not receive antiviral drug treatment during your first week of infection
• have had COVID-19 more than once

What causes long COVID?
The cause of long COVID is not fully understood. It is possible that ‘long COVID’ is not one disease, but an umbrella term for many disease processes. This would explain how it can affect people so differently. Some current theories backed up by scientific evidence are listed below:

• COVID-19 can cause damage to your organs during the first week of infection. This damage may last after the infection has cleared.
• Fragments of the virus may hide in your body after the infection has cleared. Even if these fragments can’t spread, your immune system can keep reacting to them.
• COVID-19 can make your immune system go into over-drive during the first week of infection. This can cause too much inflammation throughout the body. In some people, it stays this way even after the infection has cleared.
• COVID-19 may damage the lining of your blood vessels, and make your blood more likely to clot when it shouldn’t. This makes it hard for parts of your body to get enough oxygen.
• There are some viruses that stay in your body in a sleeping state. An example of this is Epstein Barr Virus, which causes glandular fever. COVID-19 might re-awaken these viruses.

Is long COVID the same as other post-viral conditions?

The symptoms of long COVID can overlap with other conditions.

Post-acute viral infection syndromes include the symptoms listed below. See here for more information.

• ‘brain fog’ (difficulty thinking and focusing on a task)
• disproportionate (higher than expected) levels of fatigue
• flu-like symptoms
• muscle and joint aches and pains
• poor exercise tolerance
• sensory impairment (e.g., loss of smell or taste)
• unrefreshing sleep

Chronic fatigue syndrome includes fatigue, brain fog and post-exertional malaise. See here for more information.

Is there any way to prevent long COVID?

The best way to prevent long COVID is to avoid getting COVID-19 in the first place. You can lower your chance of infection in several ways:

• wear a mask
• limit your time in crowds
• limit your time in indoor spaces without fresh air
• keep up to date with your COVID-19 vaccine boosters

If you do get COVID-19, you can lower you chance of getting long COVID by getting antiviral drugs in your first week of infection. Ask your doctor to check if you are eligible for government funding for these drugs. Getting COVID-19 vaccines can also provide some protection against getting long COVID.

How do I use the calculator if I have an ongoing medical condition that isn’t listed?
This calculator estimates your chance of getting long COVID based on the total number of listed conditions, rather than the type of conditions. This is because there is limited data available for specific conditions. If you have a condition that is not listed, we suggest you choose another condition from the list that affects a similar body part.

How do I use the calculator if I’ve had more than 4 shots?
If you’ve had more than 4 shots, select the option “2 or more boosters (4 or more shots total)”. The calculator will use data focusing on 4 shots to estimate your chance of long COVID. This will be updated when more evidence is available.

How do I use the calculator if I only had 1 shot more than 3 weeks ago?
We don’t currently have data on the effectiveness of 1 shot received more than 3 weeks ago. However, we know that effectiveness will decrease over time. For the closest estimate, we suggest that you select “None” in response to “How many COVID-19 vaccine doses have you had?”

What should I do when I’m recovering from COVID-19?
As soon as you know you have COVID-19, ask your doctor whether antiviral drugs are recommended for you. You should isolate from other people and ideally stay home. If you do go out, wear a P2 or N95 mask. Cloth and surgical masks are not as effective. You should avoid visiting places where there are vulnerable people, such as nursing homes or hospitals (unless you need medical care yourself). See here for more information.

Which antiviral drugs are included in the calculator?

The calculator considers the antiviral drugs listed below:

• Molnupiravir taken within 5 days of testing positive
• Metformin taken within 7 days of symptom onset at a dose of 1500mg immediate release taken over 6 days (Note, this may be effective at lowering risk of long COVID, but not treating the initial infection. See here for more information.)
• Metformin taken within 3 days of symptom onset at a dose of 1500mg immediate release taken over 6 days
• Nirmatrelvir (Paxlovid) taken within 5 days of testing positive

For more information on data sources, please read the document in the ‘MORE INFO’ section. For more information about antiviral drugs, eligibility criteria and cost, see the below links:

• https://www.health.gov.au/health-alerts/covid-19/treatments
• https://www.health.gov.au/topics/covid-19/oral-treatments
• https://www.covid19treatmentguidelines.nih.gov/management/clinical-management-of-adults/nonhospitalized-adults--therapeutic-management/

Where can I learn more about long COVID?

Some great resources are listed below:

• https://www.betterhealth.vic.gov.au/covid-19/long-covid
• https://www.unsw.edu.au/newsroom/news/2021/04/Long-COVID-what-is-it-and-what-do-we-know-about-it
• https://www.who.int/southeastasia/outbreaks-and-emergencies/covid-19/questions/post-covid-19-q-a
• https://hms.harvard.edu/news/most-important-question-about-long-covid
• Faux, S. (2024). Long COVID: Expert advice, from diagnosis to treatment and recovery. Murdoch Books.