Two new subvariants of the Omicron strain, the virus that causes COVID-19, are spreading rapidly. What do we know about them and how are we preparing? Our immunologist, Dr Daniel Layton, answers some common questions.

Each new dominant coronavirus variant raises questions. Are people more at risk of getting sick? Will the current vaccines still work? Are there new or different things I should do now to stay safe? Let’s find out what we know about the new Omicron subvariants.

Scientists in protective gear looking at clear containers with clear liquid in them

Scientists at our state-of-the-art biologics production facility in Melbourne work on producing and scaling-up The University of Queensland’s (UQ) vaccine candidate for COVID-19.

What are the new Omicron subvariants?

There are two new subvariants of the Omicron strain called BA.4 and BA.5. They are spreading quickly and taking over from the Omicron subvariant BA.2. To date, these subvariants have been the most common source of infections in rising cases.

Early data suggests both subvariants have arisen from the BA.2 subvariant and not the BA.1 subvariant. But it’s still early days.

Are they more contagious?

The BA.4 and BA.5 Omicron subvariants are becoming the predominant strains. They are taking over from the BA.2 subvariant. This suggests they are more contagious.

It could also be that, as a community, we have become more immune to the previous BA.2 subvariant than we are against the new subvariants.

Do our current vaccines protect against these variants?

Concerningly, researchers have found the new subvariants are more than four times more resistant to antibodies from vaccinated and boosted people when compared to the previous BA.2 variant.

This means that even if you are up-to-date on your boosters, you might still contract the virus. But the boosters will still help protect you from severe illness.

Vaccines against Omicron are in late-stage clinical trials. They will likely to be registered for use in coming months. Recent data from Moderna has shown its Omicron vaccine protects against all Omicron subvariants. However, the antibody responses are stronger against BA.1 than the BA.4 and BA.5 subvariants.

Are all new variants more contagious than the previous ones?

It might seem like each new subvariant is worse than the last. But it’s not that simple. Often new variants and subvariants emerge without detection. Or they aren’t more contagious or severe than current dominant strains. These strains typically disappear quickly.

Although many different mutations exist, only the ones that show a competitive advantage are recorded as new strains. The others die out and are not of significant interest.

How do the new variants affect cases, symptoms and hospitalisations?

So far, the new Omicron subvariants have not shown any increase in disease severity in the UK or South Africa. However, the incidence of severe disease and hospitalisation can be closely linked to the immunity of the population. This means the proportion of vaccinated and boosted people can lead to higher or lower rates of serious illness.

Should we be worried about these variants?

This third Omicron wave should not be of any greater concern than the previous waves. But any surge in cases will cause more hospitalisations and deaths.

Plus, people who have recently recovered from COVID-19 are being reinfected by the new strains. This is frustrating for those suffering symptoms again.

In the Southern Hemisphere, the rapid spread of these subvariants during the current influenza season will make this wave more difficult to manage. And co-infection with both viruses can lead to worsened disease.

The best thing we can do to protect ourselves right now is make sure our vaccinations and boosters are up-to-date.

person in protective gear conducting a PCR test

PCR tests can still detect the new Omicron subvariants.

How prevalent are these variants in Australian cases?

The numbers are changing quickly. The BA.4 and BA.5 subvariants appear to have become the dominant strains in NSW. Wastewater catchments have shown an increase from five to 40 per cent of BA.4 and BA.5 subvariants. And we expect there will be an increase in cases in Australia driven by these new subvariants.

Do RAT and PCR tests still pick up the new variants?

Yes, the PCR test can still detect the new Omicron subvariants.

Research shows the S gene (the gene for the spike protein) is not detected in one of the PCR tests for those infected with the BA.4 and BA.5 Omicron subvariant. But PCR tests typically look at multiple genes.

Some testing labs have reported that for BA.4 and BA.5 one particular PCR test experiences what is known as ‘S gene drop out’. This is where the test fails to detect the S gene, but does detect the others. Additional gene sequencing has confirmed this is a way of rapidly detecting these subvariants.

With a RAT (rapid antigen test), BA.4 and BA.5 can be detected and there is no evidence on any potential drop in accuracy.

In good news, our researchers have developed a faster and more comprehensive way to identify emerging COVID-19 variants. They do this by analysing the RNA of the whole variant, rather than the current method of monitoring changes to the spike protein.


  1. Hi Megan, thanks for your question.

    Unfortunately, based on the rate of transmission and the fact that immunity based on infection does not provide long-term broad protection, these variants of concern would have emerged even in the absence of vaccination. In this instance, our natural immunity would be putting selective pressure on the virus. The main difference is that infection without vaccination would have led to a substantially higher rate of hospitalisation and death. Additionally, without vaccination the spread of the virus would have been higher, leading to a greater chance of the emergence of a new variant.

    Team CSIRO

  2. In the early days of the pandemic, there were some scientists and epidemiologists who suggested that mass vaccination of the population was not the best response, as it creates evolutionary pressure for new variants that evade vaccines. ‘Only the ones that show a competitive advantage’ survive, as you say.
    Their recommendation was to focus instead on offering vaccination for the vulnerable population as a priority, and reduce the rise of vaccine resistant strains.
    In hindsight, would this have been a better strategy?
    Is there a risk that if we again vaccinate widely for Omicron (which is the most benign strain we have so far) , that we drive the creation of a new variant that is worse?

  3. I kept following all these things for a long time, since the beginning, but now the questions that come back to me are how we will be able to vaccinate the whole world population, and when we can see an end to this- in the midst of all other challenges.

    Environmental and human aggression also cost us lives and cause poverty. Pandemics are not easy to deal with in themselves but when combined with the troubles created by ourselves they become really tricky to get rid of.

    But I wish us luck! Big luck!

  4. Thanks for that – it’s always interesting to read things directly and not other interpretations of it.

    1. Thanks Dr Layton for the info. You mentioned being up to date with vaccines and boosters is the key, however, why no mention of masks? Studies are showing that wearing a simple N95 mask in medium-large crowds can prevent people from catching Covid. It seems like common sense to me.

  5. I would like to add that maintaining good hand hygiene by using an alcohol-based hand sanitiser and washing with soap and water, plus wearing a good quality mask (N95) at all times when outside the home and car, goes a long way to preventing infection. Maintain social distancing, and isolate as soon as you feel unwell, as infection may not show up on a RAT straight away. Do the right thing, stay home if you’re unwell, be it flu, COVID or something else, so you don’t infect others.

    1. Yes – Thankyou for this addition. I was wondering why it was not covered in the article.

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