AstraZeneca and the under 60’s: 50 shades of Grey

If you’re drawn to this article, then you’re probably looking for some information to help you make a decision regards getting your COVID vaccine. 

With the federal government seemingly saying one thing and other institutions such as ATAGI saying another, you may well be wondering what the best thing to do is? Wait for the Pfizer vaccine or get the AstraZeneca vaccine now. If you are in this quandary, then you are not alone.  

There appear to be two reasons that are making this decision difficult:   

  1. The level of risk one is likely to accept is very individual (and hence two people may make quite different choices based on the same information). 
  1. With respect to the AstraZeneca vaccine, risk/benefit changes quite significantly depending on the amount of virus within the community and the age of an individual. 

To give an example, let’s take two ends of the age spectrum eligible for the AstraZeneca vaccine and change the level of virus in the community.  

Based on Australian data, both the 18-29-year-old group and 80+ have the same risk of developing thrombosis with thrombocytopenia syndrome (TTS) from the vaccine; this is around 1.9 per 100,000 people (roughly 3% of those people die, with more severe disease reported in younger people). However, with these age groups, their risk of death and serious illness from COVID looks quite different over time (shown here as community infection over 4 months).  

For context, low circulating virus numbers would be akin to our first Australian COVID wave, medium levels would be similar to the second wave in Victoria and high levels would be similar to European infection numbers. 

18-29 year old age group 

Community infections per 100,000 Deaths prevented per 100,000 vaccines ICU admissions prevented per 100,000 vaccines Hospitalisations prevented per 100,000 vaccines 
Low (29) 0.1 
Medium (275)  0.1 1.3 10.6 
High (3544) 64 

>80 year old age group 

Community infections per 100,000Deaths prevented per 100,000 vaccinesICU admissions prevented per 100,000 vaccinesHospitalisations prevented per 100,000 vaccines 
Low (29) 6.2 1.6 11.5 
Medium (275)  183.6 5.2 260.5 
High (3544) 733 110 1239 

As you can see, the risk of developing COVID in your 80’s or 90’s at any circulating amount of virus puts you at greater risk of serious consequence and death than the vaccine, so that decision is relatively straightforward. What about an 18-year-old? When does that risk/benefit balance favour vaccination with AstraZeneca? At low levels of community infection? At medium levels?  

This is where the advice from ATAGI and the federal government differs – ATAGI’s advice is based on our current low/medium levels of community infection. The federal government wants you to make up your own mind on what acceptable risk looks like based on several variables such as (but not limited to); the volatility in community infection (especially as the virus becoming more infectious), the economic impact of illness and availability of vaccine type. 

As things stand, our current approach at yourGP is to vaccinate all those over 18 years old who opt for AstraZeneca once an informed decision around risks, benefits and alternatives has been reached. Given the small but significant risk of TTS, we will ask you to sign a consent form acknowledging that you have considered this risk and are happy to proceed to vaccination.  

To access the data for your own age group please see the link below. Please note, that this data is based on Australian vaccination and infection numbers which are low compared to global data. It also assumes that you are healthy. Any condition that puts you at higher risk of COVID complications will need to be considered separately. 

Whatever you decide, know that your GP and staff here at yourGP will endeavour to support and facilitate your decision as best we can.

Please note, that if we become able to administer Pfizer vaccines into the future, we are bound by the government rollout plan for allocation of these vaccines and will not be able to vaccinate on preference alone.   

Dr Kati Davies