All about vaccines

We put some of the most frequently asked questions about vaccines to Dr Justine Morris and Dr David Cosgriff, GPs at Osana Cremorne (pictured below)


This article was first published in northsider magazine Winter 2021. All information was correct when going to press but as Covid-19 is an ever-changing situation, please consult your doctor or healthcare professional for the most up-to-date advice on the virus and the current vaccines/treatments available in Australia.

Q: How do vaccines actually work?

A: Vaccines are a safe way to produce an immune response without causing illness. Rather than treating a disease after it occurs, vaccines prevent us from getting sick in the first place. They work with our body’s natural defences to build protection and reduce the risk of getting a disease. Traditional vaccines contain either killed or weakened versions of the virus that causes the disease, or a small part of it, such as a protein or nucleic acid. This is an antigen. Newer vaccines contain the blueprint for producing antigens instead of the antigen itself. Your immune system recognises a vaccine as foreign and responds by creating memory cells and antibodies that protect you against future infection. So if you’re exposed to the virus in the future, your immune system can quickly destroy it before you become unwell. Our immune systems are designed to remember so once exposed to one or more doses of a vaccine, we typically remain protected against a disease for years, decades or even a lifetime.

Q: How long do vaccines last and why do some need a booster?

A: The duration of immunity varies with different vaccines. Lifelong immunity is not always provided by either natural infection (getting the disease) or vaccination.


The recommended timing of vaccine doses aims to achieve the best immune protection to cover the period in life when vulnerability to the disease is highest. Many vaccines used today are relatively new and data concerning the length of time they give protection is continually being updated.


Some require multiple doses, given weeks or months apart. This can be needed to allow the production of long-lived antibodies and development of memory cells. In this way, the body is trained to fight the specific disease-causing organism, building up memory of the pathogen so as to rapidly fight it if and when exposed in the future. Most Covid-19 vaccines require two doses. Whether additional booster doses are needed is being determined by ongoing trials.


Q: How do I get a vaccine for Covid-19?

A: The Australian Technical Advisory Group on Immunisation (ATAGI) has advised on prioritisation for the rollout of the Covid-19 vaccination. This advice is consistent with guidance from the World Health Organization (WHO). We’re currently vaccinating people in Phases 1a, 1b and 2a, including all adults 50+ (as of June 2021).

On the advice of ATAGI, the Pfizer vaccine will be prioritised for people under 50. The Pfizer vaccine requires ultra-freezing and is available through large hospitals and mass vaccination centres, the first of which recently opened at Sydney Olympic Park. Bookings are available via the Government online Vaccine Eligibility Checker. Adults 40-49 are invited to register interest in the Pfizer vaccine through NSW Health and will be contacted when a booking is available.


The AstraZeneca vaccine is prioritised for those 50+. It’s available through GPs, including Osana clinics, and also some respiratory clinics.


Q: What about blood clots?

A: Rare clotting has been reported (1 in 40,000 in under 50 years and 1 in 200,000 in over 50 years) relating to the AstraZeneca vaccine. These figures show that vaccine related clotting is less common than clotting from Covid-19 itself, taking The Pill for a year or flying on a plane to London.


Q: Which Covid-19 vaccines are currently available here?

Pfizer-BioNTech is an mRNA vaccine that uses a genetic code called RNA to spark the production of the coronavirus’ spike protein. Once the mRNA enters the body’s cells, they use the instructions contained in the RNA to make the spike protein. Immune cells recognise the spike protein as foreign and begin building an immune response. The RNA from the vaccine doesn’tchange or interact with our DNA. It’s 95% effective against symptoms and 90% effective in reducing transmission. Two doses, 21 days apart. Side effects include sore arm (68%), fatigue (29%), headache (26%), muscle pain (17%) and fever/chills (7%).


AstraZeneca-Oxford is an adenovirus DNA protein-based vaccine. Protein-based vaccines use a non-infectious component of the coronavirus, usually the spike protein. Immune cells recognise this as foreign and begin building an immune response. It’s 82% effective against symptoms and 100% effective against severe disease. Two doses, 12 weeks apart. Side effects include sore arm (64%), fatigue (53%), headache (53%), muscle aches (44%), fever/chills (32%), and joint pain (26%).


Two vaccines available later this year are: Novavax is a spike protein vaccine that is 89% effective, administered in two doses, 21 days apart with similar side effects to the vaccines above.

Moderna is an mRNA vaccine and consists of two doses four weeks apart. It’s considered 90% effective with similar side effects to Pfizer-BioNTech.


Osana, 320 Military Road, Cremorne. Call 139355 for more information.