The rapidly changing landscape of RSV protection

When respiratory syncytial virus (RSV) was identified almost 70 years ago, hopes for a vaccine were quick to dawn.
 
While the wait ultimately spanned many decades, recent years have seen protection against the virus evolve rapidly in an ‘era‐defining advancement in RSV prevention’.
 
New data, released on Thursday, shows that the number of Australian babies hospitalised with RSV has nearly halved in 2025 compared to the same time last year.
 
In April 2025, just 84 babies under six months of age were admitted to major Australian hospitals with severe RSV compared to 165 in April 2024. Intensive care admissions also fell, with just 7.1% of cases requiring support, compared to 11.5% last year.
 
So, how did Australia get to this point, and what does it mean for GPs?
 
The pathogen was isolated in humans in 1957, and within a few years researchers recognised its wide impact among young children.
 
Buoyed by the success of a polio vaccine developed in the 1950s, American scientists hoped a vaccine candidate for RSV could operate on a similar principle.
 
In clinical trials in the mid-1960s, they were looking for their experimental inactivated RSV-vaccine, known as Lot 100, to teach the immune systems of participating young children to recognise and fight infection.
 
It did not. In fact, it made things worse.
 
Paul Griffin, Director of Infectious Diseases at Mater Health Services in Brisbane and Associate Professor of Medicine at the University of Queensland, believes early failures made the fight against RSV much harder.
 
‘As soon as [RSV] was discovered, there were attempts to make vaccines,’ he told newsGP.  
 
‘However, unfortunately, they were very crude and actually did the opposite of what we wanted a vaccine to do. They didn’t stop people getting it and getting unwell.
 
‘In fact, they made people who had had the vaccine and got RSV sicker, a concept known as enhanced disease.
 
‘That really put RSV vaccination back a very long way and has made it quite challenging.’
 
The Journal of the Pediatric Infectious Diseases Society describes a subsequent ‘prolonged pause’ as scientists and regulators ‘struggled to define safe and effective criteria for the advancement of candidate vaccine’.
 
According to the journal, the failure pushed RSV vaccine development efforts back until the 1990s.
 
RSV’s low profile
While momentum for a working vaccine was on ice, the virus itself did not slow down. Already known as a major cause of lower respiratory tract disease among very young children, it continued to cause spiking hospitalisations in many countries – particularly during winter.
 
In Australia alone, the National Centre for Immunisation Research and Surveillance (NCIRS) estimates there were more than 115,000 hospitalisations among patients with an RSV diagnosis from 2016–19. Of those, around three-quarters were aged younger than five, most of whom were otherwise healthy.
 
For such a widespread pathogen, however, RSV has flown under the radar compared to other common diseases. It has rarely rated a mention in mainstream publications until the last few years, a fact Associate Professor Griffin puts down to two main factors.
 
‘Until recently, we didn’t have good numbers because it wasn’t reportable, and we had no intervention,’ he said.
 
‘Most people didn’t really try and get the message out there that RSV was a significant pathogen because of those points.
 
‘But both of those two things have changed.
 
‘Since 2021 it’s reportable, so we have a much better handle on the numbers, and now we do have a number of vaccines.’
 
More protection
Those numbers, substantial from the beginning, have grown significantly. There were 95,964 notifications on the National Notifiable Disease and Surveillance System in 2022, then 128,123 in 2023 and a spike to 175,914 in 2024, although numbers so far in 2025 have slowed.
 
Crucially, clinicians now have vaccines as part of their armoury, albeit with varying access across different cohorts.  

In Australia, GSK’s Arexvy is now approved, as well as Pfizer’s Abrysvo, which is on the National Immunisation Program (NIP) for pregnant women at 28–36 weeks gestation. It became available in general practices in February this year.
 
They are also both approved for use in older patients, although the Therapeutic Goods Administration recently warned of a ‘possible but rare’ risk of Guillain-Barre Syndrome following vaccination in that cohort.
 
Neither is yet listed on the NIP for older Australians.
 
For patients early on in their lives, one randomised controlled trial found a single dose of Abrysvo is 81.8% effective in preventing severe RSV disease in the first 90 days of an infant’s life, then 69.4% effective over 180 days. A recent analysis in The Medical Journal of Australia points out that more detailed, longer-term data will be key.
 
‘As Abrysvo forms the foundation of Australia’s national RSV immunisation program, analysing hospitalisation rates in infants beyond six months of age will be pivotal in assessing the vaccine’s effectiveness over time,’ the authors wrote.
 
They also highlight the potential of monoclonal antibody nirsevimab (sold as Beyfortus), another recent arrival, to expand protection. It is now available in all states and territories for vulnerable babies.
 
Approved for use in Australia in late 2023, it is now preferred over palivizumab (sold as Synagis), which was previously the only protection on offer for children but was hampered by high costs and a requirement for frequent injections.
 
Analysis of its early impact in Western Australia, which launched the first state-wide program, show a promising reduction in RSV hospitalisations.
 
The key moments
While the vaccine approvals came shortly after the arrival of the COVID-19 pandemic, the timing is coincidental. Several pivotal moments date much further back.
 
In the 1980s, researchers found the F protein on the virus, which helps it infect human cells and can also trigger protection against the disease.
 
Scientists later realised it changes after infection, with the pre-infection F protein producing stronger neutralising antibodies. Further research at the US National Institute of Allergy and Infectious Diseases found how to freeze the protein in its pre-fusion state in 2013, paving the way for the vaccines approved so far.
 
Associate Professor Griffin, who was involved in Australian clinical trials and acts as an advisor to pharmaceutical manufacturers, is very optimistic about the difference they can make.
 
‘What’s happened in the last 15–20 years to be able to get to this point is very significant,’ he said.  
 
‘These vaccines in clinical trials and now emerging real-world evidence are very effective.’
 
For Dr Kerry Hancock, Chair of RACGP Specific Interests Respiratory Medicine, the advances have a personal meaning.
 
‘My own child ended up in hospital four years in a row with RSV infection,’ she told newsGP.
 
‘To see that we now have an RSV immunisation that I could have had in pregnancy, that would have been great – you can imagine the disruption and distress in our lives when my 10-week-old infant was hospitalised that first winter with bronchiolitis.
 
‘We are just so lucky that we do have these vaccine technologies.’
 
The founder of the Immunisation Foundation of Australia, Catherine Hughes, shares that view, describing the launch of the nationally consistent program as a ‘historic moment’.

She hopes it could prevent up to 10,000 fewer babies being hospitalised each year if its take-up is similar to the rotavirus vaccine introduced in 2007.
 
Limited access for older patients
While RSV has historically been most linked to severe disease in early childhood, the NCIRS also reports increasing hospitalisations among older adults – a trend it attributes to growing awareness of RSV and ‘more frequent laboratory testing in this age cohort’.
 
Other studies have also indicated high mortality rates among those hospitalised at this age.
 
However, Associate Professor Griffin notes the limitations of the current settings, with Arexvy and Abrysvo only privately available for older people.
 
‘Our uptake is not going to be anywhere near where we need it to be to really see the full impact,’ he said.  
 
‘But I’m confident in those people that receive that vaccine that it’s certainly going to reduce their chance of more severe disease.’
 
As for the future, he believes combined vaccines is an area to watch out for, with change possible soon.
 
‘Potentially combining with the flu and/or COVID to be able to give protection from multiple pathogens at once is probably the next big step,’ he said.
 
‘There’s a lot of work underway in clinical trials for those combination vaccines already, so it may well be only in the next year or two that we actually start to see some of those.’

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