Setting the record straight: vaccines and the Delta variant

Blog post by Professor Tracy Smart AO, Public Health Lead - ANU COVID Response
5 July 2021

Just a few weeks ago I wrote about increasing evidence that the virus is seasonal and hits hardest in the cooler months. Now, we are living it. Within a few short days, we went from minor restrictions Australia-wide to four cities locking down and others tightening restrictions.

During the week, two key themes emerged that I want to address here - the highly transmissible Delta variant and its different symptoms and all this talk about vaccination.

The Delta variant and its symptoms

This variant was the fourth variant of concern identified by the World Health Organization and emerged in India earlier this year. It is now the most dominant variant of COVID-19 in many countries, because it is much more contagious than any other strain of the virus. We know the Alpha variant (formerly known as the UK variant), was about 50 per cent more transmissible than the original strain, and it is estimated that the Delta variant is 60 per cent more transmissible than the Alpha. We have already seen evidence of this, from people contracting the virus from only fleeting contact with a positive case, to the miner in South Australia infecting his entire family including their baby. This makes it much harder to manage, which is why so many jurisdictions have gone into lockdown. There is nothing like extreme social distancing to slow the spread of an infectious disease.

The other thing you need to know is that the Delta variant appears to have a slightly different set of symptoms from those we got used to as the standard COVID-19 symptoms last year. Data from the UK COVID Symptom Study of self-reported symptoms showed that the most common symptoms for the Delta variant are headache, sore throat, runny nose, fever and a persistent cough (in this order). In other words, pretty much what you get with the common cold or flu. This reminds us again that anything that feels like the onset of a cold or flu should be considered COVID-19 until proven otherwise - stay away from work or study and get tested immediately. This is the single most important thing you can do now to protect our community against COVID-19. I'm up to eight tests so far.


The other big talking point of the week has been about vaccination. As I said in an earlier blog, I feel that we have less of a concern about vaccine hesitancy in Australia and more about complacency. In other words, people I have spoken to who are eligible for the vaccine have previously told me they would rather wait to see what happened because there was no COVID-19 in Australia. The outbreaks we are experiencing now and the Melbourne outbreak earlier in June seem to have jolted them into action, and it's great to see all sorts of vaccination records being set.

What also confused a lot of people was the Prime Minister's comments about the AstraZeneca (AZ) vaccine and particularly him saying that if people younger than 60 want the AZ vaccine, they could speak to their GP about getting it. This is not really the change in policy that it appears to be.

The Australian Technical Advisory Group on Immunisation (ATAGI) have recommended that AZ is the preferred vaccine for those over 60, and Pfizer is preferred for those under 60. This does not, and never did, forbid someone younger asking for AZ. What has changed is that an indemnity mechanism has been put in place to protect GPs who give AZ to those under 60, provided proper informed consent is undertaken.

As a result of this so-called new advice, several thousand individuals under 40 have now received their first dose of the AZ vaccine. Given the risk of getting COVID-19 in Australia is still very low despite the outbreaks, my take is that they are doing this more so to help Australia reach its vaccination targets as quickly as possible, and less to protect themselves. While I applaud their grand gesture and support their altruism, it probably isn't necessary and here is why.

The risk of developing a blood clotting condition with AZ is low at any age (and the risk of dying from that condition is considerably lower again) but this risk decreases with age. In addition, the risk of getting severe COVID-19 disease, should you become infected, increases with age. It's important to remember though that the other factor that determines risk is the risk of becoming infected in the first place. In the UK at present, that risk is pretty high for the unvaccinated. In Australia, despite our recent cases, the risk is very low. This tilts the risk-benefit equation more towards older Australians. So at present, for younger Australians the risk of developing serious complications from AZ are greater (but still very small) than the risks of developing severe COVID-19 symptoms because COVID-19 is generally less severe and you are very unlikely to become infected in the first place.

And sure - it is frustrating for people to have to wait their turn to be vaccinated due to a lack of supply of vaccine, particularly during an outbreak. But I urge patience. We have increased supplies of Pfizer coming to our shores by September. In addition, two new vaccines, Moderna and Novavax, will start to go through Therapeutic Goods Administration (TGA) processes in the coming weeks and are likely to be available before the end of the year. This means that, come summer, we will have more than enough vaccine to vaccinate all Australians, and hopefully by then we will also have the systems in place to deliver them at the same rate. It also means that, given the difference in recommended timing between doses for the two vaccines (AZ has a 12-week wait; Pfizer only three), waiting for Pfizer may mean you are fully vaccinated at the same time, or even earlier, and with less risk.

So as we live through the coming weeks and months of winter, take a deep breath, be COVID-safe, treat every cold and sniffle seriously, and hopefully the spring will bring with it a renewed sense of hope for a future without lockdowns and the threat of COVID-19.