A woman receives a COVID-19 vaccination at the Australian Sikh Association pop-up clinic in Sydney in August.
A woman receives a COVID-19 vaccination at the Australian Sikh Association pop-up clinic in Sydney in August.
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Coronavirus

Explainer

What you need to know about booster shots after new COVID-19 variant Omicron

Will the vaccines stop Omicron? The jury is still out. But experts have indicated the current vaccines and booster shots may still offer protection against the new variant.

Published Saturday 9 October 2021
By Biwa Kwan
Source: SBS News

The new COVID-19 variant, Omicron, has been designated as a variant of concern by the World Health Organization, with widespread speculation the existing COVID-19 vaccines may not be as resistant to it.

New formulations to vaccines may be needed, with Pfizer saying it could tweak its existing vaccine within 100 days and Moderna announcing it could achieve the same result by early 2022.

While the jury is still out on the efficacy of the existing vaccines against the new variant, we’re “not back at square one” according to Victoria’s Chief Health Officer Brett Sutton, with existing vaccines still providing some level of “protection against these variants as well”.

Federal Health Minister Greg Hunt on Saturday urged Australians to get the booster shots.

“If you are due for your booster, please join the now over 400,000 Australians that have had their boosters,” Mr Hunt told reporters at a press conference in Canberra.

Who will get the booster shots? 

Australia’s COVID-19 booster vaccination program kicked off in October after Mr Hunt announced the government would prioritise the 500,000 Australians with the most weakened immune systems, including people with malignant cancers, organ transplants and those born with immunodeficiencies.

Since 8 November, however, booster doses have been available to anyone aged 18 and over who has had both doses of their primary course of COVID-19 vaccine at least six months ago.

People at the Boondall mass vaccination hub in Brisbane.
Source: AAP

ATAGI is not currently recommending booster doses to people aged 12 to 17, and severely immunocompromised people who have had a third dose to complete their primary vaccination. 

How soon should you get a booster shot?

The recommended interval for the third dose for the severely immunocompromised is between two and six months after the second dose of vaccine.

In exceptional circumstances, such as an outbreak or intensification of immunosuppression, the interval may be reduced to four weeks. 

For the general population, anyone aged 18 and over should wait at least six months after their second dose.

How do booster shots work? 

The vaccine technology underlying the booster shots is the same as the first and second vaccine doses. 

Dr Emily Edwards from the Department of Immunology and Pathology at Monash University said the building blocks for booster shots draw from the knowledge developed from vaccines in the past, including for hepatitis and human papillomavirus (HPV) which form part of the immunisation programs in schools. 

"It is all about building blocks," she told SBS News in October. "The technology may have been there for years, and that is the case with the vaccines and with the immunological tools we use to monitor how you respond to the vaccine and the virus."

The booster shot is aimed at ensuring the level of immunity and protection from the earlier doses of the vaccine is maintained at a certain level as the effect from the antibodies wears off over time.  

Mr Hunt said it is important to note that two doses of the COVID-19 vaccine provide very good protection, especially against severe disease. 

"A booster dose, six or more months after the second dose, will make sure that the protection from the first doses is even stronger and longer-lasting and should help prevent spread of the virus," he said in October. 

Which booster shot should you get?

The ATAGI advice recommends the third dose to be Pfizer, which is an mRNA vaccine, irrespective of what vaccine a person received for their primary course of vaccination.

Mr Hunt said in October he expects other vaccines, including Moderna, to be added as approvals are provided by the Therapeutic Goods Administration. 

Although not preferred, AstraZeneca can be used for the third dose for those who had it for their earlier shots and did not suffer any adverse reaction, such as anaphylaxis. It can also be used for those who had a significant adverse reaction after a previous mRNA vaccine.  

How should I book?

Bookings are available for eligible people via a medical practitioner.

You can book via the government's Vaccine Clinic Finder website. 

Healthworkers at a drive-through COVID-19 vaccine hub in Melbourne.
Source: AAP

How effective are booster shots?   

Scientists are racing to find out whether or not the current vaccines offer protection against the Omicron variant.

In the case of the Delta variant, however, the vaccines continued to maintain high levels of protection against severe hospitalisation and death.

Dr Edwards said as Australian jurisdictions reopen and exit lockdown, other public health tools such as masks and physical distancing will still be necessary. But the effectiveness of vaccines still remains high - including for booster shots. 

"If you have a vaccine, you're more likely to be protected from that than someone who isn't. There will still be some infections, unfortunately. But it does mean it [may] still protect you against severe disease, which is really important, especially in this global pandemic."

Dr Quinn said studies from Israel, which moved to booster shots earlier than most nations after a rapid vaccine rollout, show that breakthrough infections were actually showing up in immunocompromised patients who were not responding to earlier vaccine doses, making the case for booster shots for this group. 

"They only make up 2 per cent of the population, this group of individuals. But, for example, in Israel, they were making up 40 per cent of the vaccinated people in hospital with COVID-19. So it is clear that we need to do more to help protect against that severe disease."

Dr Quinn said the data from Israel on the efficacy of booster shots needs more scrutiny, but anecdotal reports of booster shots on the general population show an immediate impact on hospitalisation rates. 

"And that would make sense because these third shots give an immediate boost to the immune response. It would probably provide that immediate protection. We still need to understand how durable that protection is."

She added that studies out of the UK and US demonstrate robust vaccine effectiveness in the booster shot. 

Are there any risks or side effects?

As the booster shots are the same vaccines used for the earlier shots, the advice on side effects is expected to track along the same lines. But health authorities around the world are closely observing any long-term effects. 

"The fact that other countries including the UK are six months ahead of us in terms of their vaccine regimen means we will get that information quicker and be able to respond to it in terms of timing and requirement for booster shots," Dr Edwards said in October. 

Dr Quinn said there have been small trials looking at immunocompromised people with third doses. A recent study tracked organ transplant recipients who received a third vaccine dose. 

"With this particular group of patients, there have been good studies that have shown that is clearly beneficial to receive that third dose."

Do we have enough doses for everyone? 

Mr Hunt in October said Australia is well prepared to provide booster doses. 

"With over 151 million Pfizer, Novavax and Moderna vaccines already secured for supply into the future, Australia is well prepared to provide booster doses as approvals are provided by the medical experts," he said. 

Infectious diseases expert Sanjaya Senanayake has previously said internationally, the discussion of booster shots in rich nations has put the spotlight on vaccine equity as it applies to the provision of first and second doses for developed nations.

"At the end of the day, if we're protected from severe illness and hospitalisation [in Australia], we should try and help the rest of the world," he said. "We have to be selfless to be selfish when it comes to COVID-19 and vaccination," he added, referring to herd or population-wide immunity in the Asia-Pacific region. 

Additional reporting: Shuba Krishnan

Read more from the Vaccine in Focus series.


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