Dialog Box

Rare Cancers Australia

Can we trust COVID-19 vaccines?

As the pandemic continues to evolve, and as does our response, there is a great deal of misinformation circulating as we all try to keep up with the latest advice and developments. Of particular concern to our community is COVID-19 vaccine safety and efficacy.

We can address this by breaking this down into three questions.

How do COVID-19 vaccines work?

There are currently two COVID-19 vaccines in Australia – AstraZeneca and Pfizer. 

  • The AstraZeneca vaccine uses an inactive common cold virus as the vehicle to transport the instructions for the harmless spike protein that exists on the surface of the coronavirus.

    This is injected into our muscle which transports the “instructions” on how to make the spike protein into our cells (not into the nucleus of our cells, where our DNA is) so that our body's immune system can familiarise itself with these non-infectious spike proteins, and produce antibodies that remember what they look like. This immune memory is imperative so that next time your body is exposed to the real coronavirus spike protein, it already is aware that it's a foreign “enemy”, and it is primed and ready to attack.

    The AstraZeneca COVID-19 vaccine is 95% effective in protecting us against severe disease, and 92% effective against the Delta variant.

  • The Pfizer vaccine uses mRNA technology to fight the infection.

    mRNA, or messengerRNA, is actually a messenger molecule that's been in every living cell for billions of years. It is the protein that translates short “messages” of information from your DNA in the nucleus of your cells so that the proteins can be assembled in order to carry out the many processes necessary for the body to function. mRNA instructions are timed to “self-destruct” after they've been read and translated into proteins - as a safety mechanism to control the rate of protein production.

    In relation to the Pfizer vaccine, it uses mRNA to introduce a message with a code which triggers the release of the coronavirus spike protein - just enough to get a person's immune system to generate antibodies that will protect them if they are later exposed to the real virus. After this, the mRNA is destroyed and eliminated from the body in less than 72 hours.

    mRNA hasn't been used in vaccines before now as they have never been able to find a reliable way of transporting the fragile mRNA into a person's cell. But it has been developed and used in other medical technology for approximately 15 years.

    The Pfizer COVID-19 vaccine is 93% to 98% effective in protecting us from hospitalisation and death from COVID-19, including the Delta variant.  

Both vaccines, once both doses have been given, protect against hospitalisation and death, and reduce transmission by up to 70%. 

Neither contain implants, microchips, tracking devices, or the live SARS-CoV-2 virus. 

What are the side effects?

As with any vaccine, you may have some temporary side effects after receiving a COVID-19 vaccine. 

The most common side effects from the Pfizer and AstraZeneca vaccines are generally mild. They can include symptoms like a sore arm, headache, mild fever, muscular aches and pains and fatigue. 

In some cases, people can experience enlarged lymph nodes, nausea, diarrhea and itchiness, however this usually passes in one to two days. 

Serious side effects are rare and can include myocarditis, which is inflammation of the heart wall, following the Pfizer vaccine. Thrombosis with Thrombocytopaenia Syndrome (TTS), which involves blood clots, can occur following the AstraZeneca vaccine. However, overall, the chances of experiencing these serious side effects are minuscule, especially compared to the risks of COVID-19 infection and its consequences.  

In relation to TTS, there is a 1 to 2/100,000 (depending on age) chance of experiencing this complication with the 1st dose of AstraZeneca in people under the age of 60, and there is a 1/1,000,000 chance with the 2nd dose.

However, COVID-19 infection can be very serious, no matter the age group, especially with the Delta variant that is currently circulating. Less than 99% of people hospitalised with COVID-19 are unvaccinated or only half vaccinated, and the long-term effects of COVID-19 infection are becoming more apparent - half of those hospitalised still have persistent symptoms after six months, and 27% of young people admitted to hospital with COVID-19 suffer some kind of organ failure. This is what we know so far – we still we don't know what will happen in the years to come.

How do we know the COVID-19 vaccines safe?

Both the Pfizer and AstraZeneca COVID-19 vaccines have been approved by the Therapeutic Goods Administration (TGA) following completion of all safety trials - including phase I, II and II clinical trials.

There is some commentary around how fast these vaccines have received approval, and whether this means safety has been compromised.

However, both Pfizer and AstraZeneca use long-standing technology to prime our immune systems, and they have both undergone the usual safety checks and clinical trial phases – just in a quicker period of time.

In this process, the science has not been fast-tracked. The administration and funding processes behind it have been accelerated and unfortunately, this has been due to the urgency with which we need to act against a virus that spreads so rapidly. This has also resulted in comprehensive data being available much more quickly due to the tens of millions of COVID-19 cases globally, and the constantly evolving real world evidence, which has continued to inform best practice; as opposed to the usual vaccine phase III clinical trial only involving tens of thousands of cases.

You can find out more information about how the COVID-19 vaccines have been tested and approved in Australia on the Australian Government's website.

  • Fernando P. Polack, Stephen J. Thomas, Nicholas Kitchin, et al. (2020) Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. N Engl J Med 383:2603-2615  
  • Tariq Azamgarhi, Michelle Hodgkinson, Ashik Shah, John A. Skinner, Iva Hauptmannova, Tim W. R. Briggs, Simon Warren. (2021) BNT162b2 vaccine uptake and effectiveness in UK healthcare workers – a single centre cohort study. Nature Communications 12:1
  • Ian McDonald, Sam M. Murray, Catherine J. Reynolds, Daniel M. Altmann, Rosemary J. Boyton. (2021) Comparative systematic review and meta-analysis of reactogenicity, immunogenicity and efficacy of vaccines against SARS-CoV-2. npj Vaccines 6:1
  • John P. A. Ioannidis. (2021) Benefit of COVID-19 vaccination accounting for potential risk compensation. npj Vaccines 6:1
  • Pablo M. De Salazar, Nicholas B. Link, Karuna Lamarca, Mauricio Santillana. (2021) High coverage COVID-19 mRNA vaccination rapidly controls SARS-CoV-2 transmission in long-term care facilities. Communications Medicine 1:1
  • Pratibha Anand, Vincent P. Stahel. (2021) The safety of Covid-19 mRNA vaccines: a review. Patient Safety in Surgery 15:1
  • Matan Levine-Tiefenbrun, Idan Yelin, Rachel Katz, et al. (2021) Initial report of decreased SARS-CoV-2 viral load after inoculation with the BNT162b2 vaccine. Nat Med 27, 790–792

12 August 2021
Category: News
Tags: astrazeneca, connect, Coronavirus, COVID, covid connect, covid information, covid vaccine, Covid-19, Dr Emily, Dr Emily Isham, how do covid-19 vaccines work, pfizer, vaccine efficacy, vaccine side effects, vaccines,