At the present date (the start of September), Australia has two vaccine candidates which the public can have. While it’s good to know about each of them, in many ways the community discussion about these two vaccines can lead to stress due to desiring one over another. The stress is because, due to worldwide supply chain constraints we only get a certain amount of vaccines delivered to Australia. Consequently the government, on advice of ATAGI (their technical group that advises on vaccinations) only has supplies for Pfizer for people aged 16-59 years old inclusive and 12-15 years old with specified medical conditions. There appears to be ample Astra Zeneca COVID-19 vaccinations to vaccinate anyone (18 years or older) who would like to get it, on the basis of informed consent.
Common side effects after vaccination:
These usually occur in first 12 to 72 hours (sometimes longer), and included, but are not limited to:
- Sore arm at vaccination site
- Flu like symptoms
- Body, muscle, joint aches
- Fever, sometimes chills
- Mild headache
Roughly half of people get some form of reaction, some get essentially no reaction, a small portion of people have reactions lasting longer than 72 hours. The reactions are often worse after the first dose of AstraZeneca and worse after the second dose of Pfizer.
Rare side effects with AstraZeneca
As at 15th August, with 8.1 million doses of AstraZeneca vaccine given in Australia there were 112 reports of blood clots possibly or confirmed related to the vaccine. This means the odds of Thrombosis with Thrombocytopaenia Syndrome (TTS) are roughly 1:70,000 (depending on age) and the risk of dying from this is approximately 1:1,000,000.
To put this in some context, your risk of dying from a car accident at some point in your life is about 1:20,000 (of course risk is more nuanced than simply this comparison, in giving a vaccination a medication is given to a “well” person to prevent a possible disease, giving a medication to a “well” person should meet a higher threshold than giving a medication to someone who is “sick”).
It’s worth noting that the risk of a blood clot from the contraceptive pill is 1:1000 – a DVT. To our current medical knowledge, there is not an overlap between risk for DVT and TTS (thrombosis with thrombocytopaenia syndrome).
TTS may be seen from day 4 until day 42. It can present with the following symptoms (but not limited to):
- Blurred vision
- Reduced consciousness
- Abdominal pain
- Leg pain
It requires urgent medical assessment with GP or emergency department, and can be diagnosed with a simple blood test.
Rare side effect after Pfizer
The most common rare, but significant side effect from the Pfizer vaccination that we know of is Myocarditis or Pericarditis. This can present with symptoms including (but not limited to):
- Chest pain
- Shortness of breath
- Rapid heart beat or palpitations (arrhythmias) of the heart
- Swelling of the feet, ankles or legs
- Generalised symptoms of an infection, such as headache, body aches, joint pain, fever, sore throat or diarrhoea
Out of the 7.2 million doses of the Pfizer vaccine administered at 15th August there were 188 suspected cases of myocarditis or pericarditis, and no deaths. Most of these cases are mild. That is a risk of approximately 1:40,000. Young people with structural heart disease or arrhythmias are encouraged to seek their cardiologist’s advice before a Pfizer vaccination.
If the above symptoms develop, urgent medical assessment should be sought via a general practitioner, emergency department or cardiologist and tests which include an ECG, cardiac enzymes and echocardiogram can be done to assist the diagnosis.
Comparison of effectiveness:
Pfizer is slightly better at preventing symptomatic COVID (cold-like or flu-like symptoms) – 95% protection after the 2nd dose. With AstraZeneca it is approximately 60% if the booster is at 6 weeks and approximately 80% if the booster is at 12 weeks.
However, the purpose of the vaccination is protection from severe COVID-19 (which is hospitalisation, or being on a ventilator in hospital) or death. Both vaccines give at least 95% protection from severe COVID and death.
So… if the purpose is to prevent severe COVID (which many would argue), they are both similar in effectiveness.
The risk of a severe or fatal outcome from COVID-19 is much lower in young people, therefore the relative risk of adverse reaction from the AstraZeneca vaccine is higher.
Of course in the context of an “outbreak” the risk of COVID 19, and a severe outcome from the disease itself increases.
Immunity to coronaviruses wanes over time (eg: 6 months), whether that immunity is from an acquired infection or by vaccination. A recent study showed that the immunity waned more slowly with the AstraZeneca vaccination than with the Pfizer vaccination.
There are so many different variables, many different pros and cons for each vaccination and this discussion could go for hours or more. It’s very difficult to work out the odds of benefit / risk for any individual person.
Current Government Guidelines re: Pfizer and AstraZenica
As at the current date, due to supply chain constraints, we can only vaccinate people between the ages of 16-59 with Pfizer and those with specified medical conditions outside those ages.
Pregnant women who get COVID-19 have an increased risk of severe illness and adverse pregnancy outcomes, and are a priority to get vaccinated with the Pfizer vaccination. A recent information release from Chief Medical Officer for NSW, Dr Kerry Chant, says there is no evidence to date that COVID-19 vaccination affects the ability to conceive.
Most general practices have plenty of AstraZeneca to give right away, and can begin patients on the journey to being “fully” vaccinated. Those practices are bit by bit working through eligible patients for Pfizer first, and it will take longer to get a Pfizer vaccination. It may be at least a month or two before we can offer Pfizer outside the current guidelines – that is pure speculation on my part. This means that each individual who chooses to get vaccinated is likely to be faced with discerning the choice between getting AstraZeneca now, or at least some weeks to start a Pfizer vaccination course.
Most general practices are receiving very many requests every day, to vaccinate people outside the government guidelines we are given. We are obliged to stick within the guidelines.
The government “encouragement” is to get whatever vaccine you can get as soon as you can get it – to protect yourself from COVID-19 and also as a community service to protect others.
If you need to consider your options and are looking for a discerning read: Google: “Doing the maths on AstraZeneca” is a helpful article to see how a scientist weighed up whether to get AstraZeneca or not<https://www.smh.com.au/national/doing-the-maths-on-astrazeneca-20210727-p58d81.html?btis>