COVID risk calculator updated to include Pfizer vaccine, myocarditis probability

Anastasia Tsirtsakis

10/01/2022 2:00:02 PM

New data has been added to the online tool, which is designed to help GPs and their patients assess the risks and benefits of vaccination.

GP talking to patient.
GPs can also access a matrix featuring all the risks on one single chart.

Almost 12 months into Australia’s COVID vaccination rollout and the benefits are undeniable.
Despite there being more than 200,000 active cases, a minority of those infected are requiring hospitalisation and an even smaller number escalation to ICU, with most able to be managed in the community.
But as the booster rollout gains momentum, and a growing number of children and adolescents step forward to be vaccinated, there are some who continue to grapple with concerns related to adverse events.
To assist GPs with the task, the team behind the Immunisation Coalition COVID-19 Risk Calculator (CoRiCal) have updated the online tool that is designed to help patients assess the risks and benefits of vaccination.
Previously focused on the AstraZeneca vaccine, the latest update includes data on Pfizer and its efficacy against infection and death, as well as the probability of developing myocarditis.
A collaboration with UQ, QUT, and Flinders University, the tool was developed with a range of expertise, including CoRiCal co-chairs, Melbourne GP Professor Andrew Baird and retired GP and public health physician Associate Professor John Litt.
UQ Professor Colleen Lau, who helped develop the model, previously worked as a GP for 15 years and says she understands firsthand the challenges her colleagues have been facing in their consultation rooms.
She says the calculator will be particularly useful for patients who are still sitting on the fence about vaccination, including certain ethnic groups with low vaccine uptake who may benefit from the visual tool. 
‘There are anti-vaxxers where it’s going to be very difficult to convince them regardless of what evidence you have,’ Professor Lau told newsGP.
‘But for people who are generally concerned about side effects and just trying to get more information to weigh up the benefits, having a risk chart at the consultation can be really helpful.’
Patients can also use CoRiCal in their own time to assess the benefits and risks for them personally based on their age, sex, current community transmission scenario and vaccination status. The calculator offers average estimates on their risk of contracting COVID-19 and dying from it, while comparing that to the risks and benefits of vaccination.
While the risk of myocarditis is rare, the Therapeutic Goods Administrations notes the incidence has continued to increase slightly, occurring at a rate of 1–2 per 100,000 Pfizer doses. However, it is more common after a second dose for teenage boys, at a rate of 11.8 per 100,000.
Though CoRiCal is aimed at adults, it does include data on 12–19-year-olds to put the risks into perspective.
For example, in a setting with high transmission, an unvaccinated male aged 12–19 has a one in 37 chance of contracting COVID. That risk is reduced to one in 79 after one dose of Pfizer received less than three weeks ago, down to one in 340 for those who received two doses less than two months ago.
That is in contrast with the chance of developing vaccine-associated myocarditis after one dose (one in 42,000) and one in 9700 after the second dose – a risk the tool contextualises by comparing it with the lifetime chance of dying as a result of choking on food, which is one in 5000.
Meanwhile, the chance of a male aged 12–19 dying from myocarditis is one in 12 million after one dose and one in 2.8 million after two doses.
The risk of myocarditis in this cohort is, however, higher following Moderna, with a rate of 16.8 cases per 100,000 second doses in this cohort. Professor Lau says there are plans to include data on Moderna, but that at present, it is lacking.
To make using the data as simple as possible for GPs, the infectious diseases expert has also designed a matrix, using the same formatting as the Absolute Cardiovascular Risk Calculator that GPs are familiar with, featuring all the risks on one single chart.
The above matrix uses the same formatting as the Absolute Cardiovascular Risk Calculator and features all the risks in chart. (Image: Supplied)

And with the vaccine rollout having now commenced for children aged 5–11, the team is currently working on a similar online tool specifically focused on adolescents and children, which could help to allay any concerns parents may have.
As the pandemic rapidly evolves in Australia, Professor Lau says there are plans to continue updating CoRiCal to reflect the latest data, as well as further personalising the tool to include risks and benefits for people with various comorbidities.
‘But as you can imagine, it’s quite a lot of work to update these things and the availability of data is probably the biggest limitation,’ she said.
The most pressing update, however, is likely to be the community transmission scenarios. Currently, the highest risk available is based on 2500 infections per day in New South Wales, where infection rates have since surpassed 38,000 per day.
‘When we first built this tool … people were saying “2500 per day is unrealistic, it’s never going to happen”. But, of course, we’re way beyond that now, so we’re going to add in very high and extreme transmission,’ Professor Lau said.
‘But that probably won’t change the outputs that much in the sense that already now the model shows that the benefits of the vaccine far outweigh the risks. So when there’s even higher transmission, then the benefits are even greater.’
Though the calculations are currently based on the Delta variant – with plans to update it as more understanding and data on Omicron becomes available – even if the age distribution of cases and case fatality rates differ, Professor Lau imagines the main message will remain the same.
‘You can easily see that the unvaccinated, regardless of age and sex, are much more likely to die if they get COVID,’ she said.
‘Whereas people who have had three doses are much less likely to die – that message is not going to change.’
The COVID-19 Risk Calculator (CoRiCal) can be accessed on the Immunisation Coalition website.
Log in below to join the conversation.

COVID-19 myocarditis Pfizer vaccination

newsGP weekly poll As an international medical graduate, what was your primary reason for wanting to practise in Australia?

newsGP weekly poll As an international medical graduate, what was your primary reason for wanting to practise in Australia?



Login to comment

Dr Ian   11/01/2022 10:34:06 AM

We are waiting for Novovax and the other protein based vaccines .
Australia has bought millions enough to give to those who get myocarditis on first dose for second dose or second dose for third dose .
Also it may be preferred for young males if the production hopes can be reached .