Photo by Parang Mehta on Unsplash
Photo by Parang Mehta on Unsplash

EXPERT REACTION: ATAGI recommends second 'winter booster dose' for vulnerable Australians

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The Australian Technical Advisory Group on Immunisation (ATAGI) has released recommendations for a fourth 'winter' dose of COVID-19 vaccines. The group is encouraging adults aged 65 years and older, Aboriginal and Torres Strait Islander people aged 50 years and older, aged and disability care residents and severely immunocompromised adults to get their fourth dose, four months or more after their third.

Organisation/s: Australian Science Media Centre

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Cassandra Berry is a Professor of Viral Immunology at Murdoch University

Winter is coming to the Southern hemisphere, and we can expect a bad flu season. With hard border controls, we have prevented many flu strains coming into Australia until now. However, we are still in a COVID pandemic with more SARS-CoV2 virus circulating than ever before. So, it is vital for people to stay immune and get this year’s updated flu vaccine for protection.

Without immunity, we simply lose the war against these respiratory viruses. Once flu enters our body it essentially cracks our epithelial cell lining and opens our airways for different invading pathogens, like Omicron BA.2. If this happens, we will likely observe much higher numbers of hospitalisations.

So, getting a fourth dose as a booster for those with poor or waning immunity is critical and will reduce the number of deaths. Those aged over 65, immunosuppressed or immunocompromised and Aboriginal or Torres Strait Islanders should be eligible now as we head into winter. Expanding the eligibility for this fourth dose to other adults would also be beneficial as our neutralising antibody levels decline.

There are no concerns for people getting more doses of the COVID-19 vaccine. We currently recommend yearly flu shots and hopefully a new combination COVID-Flu vaccine will be available as an annual booster for the community.

Last updated: 25 Mar 2022 5:05pm
Declared conflicts of interest:
Cassandra has declared she has no conflicts of interest
Professor Jeremy Nicholson is Pro Vice Chancellor of the Murdoch University Health Futures Institute and Director of the Australian National Phenome Centre

The Omicron sub-variants of SARS COV-2 have proved to be much more infectious than earlier variants and require at least a third vaccination dose to be protective. This applies to all vaccines. Interestingly the third or booster dose produces a very strong and rapid antibody response,  but the antibody levels start to decline from about four to six months.

Given that many of the elderly and at risk groups were vaccinated early they are less well protected now and urgently need a fourth dose, particularly as winter is in its way and there is a possibility of a surge of the omicron BA2 subvariant which has happened in other countries and is happening right now in the UK.

Australians have become complacent about COVID-19 but the virus continues to evolve and still poses a long term threat. Vaccination does not protect completely but it demonstrably reduces severity and probably long COVID-19 as well. 

My view is that the fourth vaccine dose will be important in minimising hospitalisations in the coming months and should be extended to younger population groups as well.

Last updated: 25 Mar 2022 4:37pm
Declared conflicts of interest:
Jeremy has declared he has no conflicts of interest.

Dr Vinod Balasubramaniam is a virologist at the Jeffrey Cheah School of Medicine & Health Sciences at Monash University Malaysia

The ultimate goal of vaccination (including booster shots) is to prevent severe illness and death, not mild infections, and current data around the world show the shots still are doing a good job at that.

During the Omicron wave, effectiveness against hospitalization was 91 per cent in people who had gotten their booster two months earlier, and 78 per cent by the fourth month after that booster. In addition to that, the vaccine efficacy against requirement for emergency department visits for COVID-19 symptoms followed a similar decline, from 87 per cent up to two months after the booster to 66 per cent four to five months after the booster (data from CDC).

While the protection that we are getting from the third shot (booster dose), is good enough to prevent hospitalisations and deaths, It’s not that good against infections. In some people, especially in the elderly and immunocompromised individuals, individuals with comorbidities these infections may lead to a more profound symptoms (if the effectiveness from the previous booster shots continues to drop even further in time).  Pfizer’s recommendation for a fourth shot of its COVID vaccine was based on the recent study in Israel [currently available as a preprint].

Israel began administering a fourth dose to older adults, health workers and people with compromised immune systems in late December as the Omicron variant spread quickly through the population. Since then, almost 600,000 Israelis have received the extra dose. The researchers found that those who had the fourth dose had twice the protection from infection as the others, and at least three times the protection from severe illness and did not show any major concerns in terms of adverse effects (reactogenicity profile) when compared to the third dose.

Overall, in time, especially more than six months after the booster doses are given, if the booster shot (third dose) effectiveness against hospitalization, severe disease and symptoms, requirement for emergency department visits drops even further to maybe 50 per cent, we must give serious consideration for giving a fourth boost to the elderly and those with certain underlying health conditions (as mentioned above).

Last updated: 25 Mar 2022 4:13pm
Declared conflicts of interest:
Vinod has declared he has no conflicts of interest.
Professor Peter Richmond is Head of the Vaccine Trial Group at the Wesfarmers Centre of Vaccines and Infectious Diseases at Telethon Kids Institute

How effective does a fourth dose appear to be?

From studies completed overseas, booster vaccination has proven to be very successful in protecting against severe disease (including Delta variant) and hospitalisation. There is a need for further research to evaluate the durability of protection offered by vaccination, particularly in vulnerable groups, and the cross-protection offered against SARS-CoV-2 and its variants (including Omicron and additional variants that might emerge in the future), which is why we are currently conducting our own research to gain our own data here in Australia.

Would there be a benefit to expanding the eligibility for this fourth dose down the track?

We have just launched the Platform Trial in COVID-19 Vaccine Boosting (PICOBOO), which will investigate whether immunity can be maximised by “mixing” vaccine booster types and how long this protection lasts, as well as evaluate how strategies may need to differ depending on age and previously administered COVID-19 vaccines. We plan to expand this platform study to include additional groups in the future, including third dose boosting in children (5-11 years) and adolescents (12-17 years). 

People are also seeking answers on what the future holds with COVID-19 as a regular fixture in our lives, such as if there will be a need for an annual COVID-19 vaccine like influenza and if booster vaccinations will be required before travelling overseas to places where other strains may be dominant. This research will play a vital role in answering questions around 4th doses for everyone and ensuring we have the best possible COVID-19 vaccine strategy for all Australians going forward, as well as providing ongoing surveillance to tailor the program as additional variants of the virus emerge and new vaccines become available.

Last updated: 25 Mar 2022 12:25pm
Declared conflicts of interest:
None declared.
Professor Raina MacIntyre is Head of the Biosecurity Program at the Kirby Institute at the University of NSW. She is an expert in influenza and emerging infectious diseases.

This is welcome news. Protection from three doses wanes substantially after a few months, even against severe outcomes like hospitalisation and death. A fourth dose brings immunity back up to levels similar or a little higher than early after the third dose. Without a fourth dose, there is little protection against symptomatic infection – a fourth dose raises this to 31-43 per cent which is important on a population level.

The vaccine is against the Wuhan strain, and Omicron is very different to the original strain, so there is immune evasion. As such, the modest effectiveness is a good result. The impact of vaccines is a function of vaccine efficacy, coverage and incidence of infection. When incidence is high, even a vaccine of modest efficacy can have a major population impact. With no attention to safe indoor air and mask mandates dropped, this becomes even more important.

I would have liked to see a fourth dose available to anyone over 50, because at 50 years, the immune system starts to decline in a process called immunosenescence, and it declines exponentially and predictably from then on. This has been well studied for other infections and COVID-19 seems to follow the same pattern. We now need to get third dose rates up to 90 per cent or higher – the rate of third doses is still too low at around 68 per cent; and ensure people in aged care facilities and other recommended groups get their fourth dose as soon as they are eligible.

This is not a cold or the flu. There is now substantial evidence of serious long term effects including brain damage, heart disease, lung disease and diabetes in a proportion of survivors, even in people with mild infection. This matters for younger people, who have their whole life ahead of them. So everyone 16 and over should ensure they get their third dose, and over 65 their fourth dose. For people who do not wish to get infected repeatedly and risk these complications, a fourth dose, attention to safe indoor air and use of a high-quality mask gives a reasonable chance to avoid COVID-19.

Last updated: 25 Mar 2022 12:22pm
Declared conflicts of interest:
None declared.
Professor Adrian Esterman is Chair of Biostatistics at the University of South Australia

Until now, only people with a select group of conditions severely impacting their immune systems could get a fourth dose. With many state and territory governments relaxing public health measures, this has put a much wider group of people with impaired immune systems not currently eligible for the fourth dose, at high risk of infection and severe illness, especially as winter approaches. This group includes those over 65, residential age care residents, and those with a much wider group of health conditions that impact their immune systems. 

ATAGI has been looking for some time at whether to expand the group eligible for a fourth dose and has been in close contact with the UK and Israeli governments who already provide a fourth dose to a much wider group of people.

It appears that for most people, a third dose is optimal, providing protection from serious illness for many months. For these younger fit people, it is therefore unlikely that a fourth dose will be recommended any time soon. 

A fourth dose will now be available from the 4th of April to those aged 65 and over, and those with health conditions putting them at risk of serious COVID-19 illness, with the proviso that it has to be four months after the third dose. Although mRNA vaccines are recommended, AstraZeneca and Novavax will be allowed if for any reason someone cannot have an mRNA vaccine. 

The fourth dose will restore protection against infection and symptomatic disease for this vulnerable group for several weeks and will provide longer term protection against serious illness and death.

Last updated: 25 Mar 2022 12:22pm
Declared conflicts of interest:
None declared.
Dr Daniel Layton is an immunologist at CSIRO

Not all immune responses are created equal. Particularly, as we age we see a decline in our ability to mount a strong and lasting immune response. Given COVID-19 disproportionately impacts the elderly, it is critical that during our winter months they have the best protection possible.  

Boosting the immunity of those most at risk as we head into winter in the southern hemisphere will support immune responses to be at their peak, not in decline. This will reduce the disease burden in these populations should we see another spike in cases. 

For people with severe immunodeficiency, the ability for their immune system to generate a protective response to a vaccine is diminished. This can be due to several reasons including medical treatments such as those given for cancer, genetic immune disorders and prolonged illness. They are particularly vulnerable both because of low immune response to vaccines as well as a reduced ability to fight the virus naturally. Giving additional boosts in this instance will ensure the best chance of reduced disease.

Last updated: 25 Mar 2022 12:21pm
Declared conflicts of interest:
Daniel has declared he has no conflicts of interest.
Dr Roger Lord is a senior lecturer (Medical Sciences) with the Faculty of Health Sciences at The Australian Catholic University and Visiting Research Fellow with The Prince Charles Hospital (Brisbane)

The new advice from ATAGI regarding a fourth dose of one of the approved COVID-19 vaccines for those aged 65 or over (including age care residents), Aboriginal or Torres Strait Islander people aged 50 or over and severely immunocompromised adults is very important.

recent peer-reviewed publication in the journal, Nature Microbiology, examined the antibody response to COVID-19 vaccination with either the AstraZeneca or Pfizer vaccines in 45,965 adults from the general population of the United Kingdom. One of the important findings from this study was that people aged 75 years or older were less likely to produce an appropriate antibody response following vaccination. 

Some people fail to generate an antibody response following vaccination, and this can happen to individuals of any age and thought to be related to a person’s genetic background. Failure to generate a response is however more marked as we age and raises the question of whether antibody response should be measured following vaccination in the aged or those who are immunocompromised. 

If no antibody response is evident after three doses of a vaccine then a fourth dose may not provide any additional benefit. Additionally, where no antibody response has been achieved with one type of COVID-19 vaccine changing the type of vaccine the person receives might produce a better response (e.g. early doses with AstraZeneca then boost with Moderna).

In Australia, much media attention has been made of the high rate of COVID-19 deaths in nursing homes because of low vaccination rates in some areas. It is equally important to consider if an antibody response was generated following vaccination rather than assume one has occurred before considering if further vaccination is going to be beneficial or if consideration is required as to the type of COVID-19 vaccine a person should be offered.

Last updated: 25 Mar 2022 12:19pm
Declared conflicts of interest:
None declared.

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