Since the start of February, pregnant women have been eligible to get vaccinated against respiratory syncytial virus (RSV).
The vaccine is administered during the 28 to 36 week mark of pregnancy to protect newborns from RSV.
As of June, more than 60,000 women had received the vaccine.
Guest/s
- Professor Jim Buttery, Murdoch Children's Research Institute and infectious diseases physician at the Royal Children's Hospital in Melbourne
References
Olivia Willis: First though, we're in the middle of winter, which means, along with colds and flu and COVID-19, RSV, a highly infectious virus, is spreading once again. However, this year it seems, Norman, that case numbers are a little down, particularly in very young children, and that follows the introduction of the maternal RSV vaccine in pregnant women. The vaccine was rolled out for the first time in February this year. And to find out what impact it's having on RSV infections and hospitalisations, I spoke to Professor Jim Buttery, head of Epidemiology Informatics at the Murdoch Children's Research Institute, and an infectious diseases physician at the Royal Children's Hospital in Melbourne.
Jim Buttery: In Australia we know that it particularly affects the very young and the very old, and we know that in children under two, more than 1,100 children are admitted to hospital each year with severe RSV infection, and almost 10% of those children end up in intensive care. The reason young children are particularly affected is because RSV particularly affects the small airways, and children, with their much smaller size and much smaller airways, are especially affected.
Olivia Willis: And in February this year, for the first time a maternal RSV vaccine was introduced nationally. Can you tell me about what stage of pregnancy the vaccine is recommended and how effective it is?
Jim Buttery: So the vaccine is recommended from 28 weeks gestation in pregnancy, up to 36 weeks. It's been introduced in many countries around the world, and so both from the clinical trials and from the countries where we have effectiveness information, it is highly effective in protecting babies for the first three to six months of their lives in developing severe RSV infection causing them to go to the doctor or to go to the hospital.
Olivia Willis: And how does the vaccine work? Does it transfer antibodies from the mother to the child?
Jim Buttery: Absolutely. So when we vaccinate the mother, the mother makes an immune response, as she does to any vaccine, and the antibodies that she makes as part of that immune response are passed through the placenta to the baby in the same way that all of mum's learned immunity protects baby against a whole variety of infections that the baby's likely to encounter for the first six months of their life. And interestingly the baby ends up with a high level of antibody than mum, because part of that protective mechanism actively transports the antibody across the placenta.
Olivia Willis: So the vaccine was introduced nationally in February. What do we know about the uptake of the vaccine so far?
Jim Buttery: We don't have full information so far, but the early information is that the uptake has been quite high. So in Victoria we've estimated to have about a 66% to 68% coverage for mothers who've been delivering, and that looks similar to elsewhere in Australia where it looks to be running in the highly 60% to 70% range.
Olivia Willis: The federal government actually put out some data in June which said that about 60,000 women so far had received vaccine, 60,000 pregnant women, which does seem pretty high in terms of from, you know, February to June, that the majority, it suggests, are accepting vaccination in pregnancy.
Jim Buttery: The initial data has been really encouraging. We know from our experience with other vaccines in pregnancy, including whooping cough vaccine and influenza vaccine, that the mothers are very motivated to receive vaccines that they believe will protect their baby, especially early in life.
Olivia Willis: So in saying that, the institute that you work at, the Murdoch Children's Research Institute, they are running a study looking at parent decision making around the RSV vaccine in particular for pregnant women, and also at a preventative treatment that's given to children, which I want to talk to you about in a moment. On this study, what have you found so far?
Jim Buttery: So we're still analysing the results, but what we've been interviewing is prospective parents around (given that there is both the vaccine as well as the highly effective antibody product that's given to the baby) what would influence their decision making regarding having a preventive therapy against RSV? And that helps inform the best way that we should be offering this protection to parents, and also at what times and where.
Olivia Willis: On this question of vaccine acceptance and in some cases hesitancy, one of the concerns that I've seen raised around the RSV vaccine for pregnant women, and we've actually had a few people get in touch with the show with questions about this, is the risk of preterm birth and whether this is increased as a result of the RSV vaccine. Can you tell me about that and what studies tell us about that risk?
Jim Buttery: Yeah, so this is an important question. So there were two vaccines developed during very carefully conducted trials in pregnancy. The first vaccine, the trial was discontinued due to a signal that there was an increased rate of premature deliveries in the vaccine arm compared to the placebo arm, and that vaccine has never been used in pregnant women since then. That was a small signal, but nevertheless there was a difference. The other vaccine, the vaccine we're using now, did not show any significant increase in pre-term labour during the trials. And most importantly, since its introduction in a number of countries, and in particular in the US where they're regularly conducting analysis to make sure that there's no increase in prematurity, so far there has been no sign that pre-term delivery is more likely in women who receive the vaccine compared to women who don't. So the initial results have been extremely encouraging.
Olivia Willis: So in addition to the maternal vaccine, there is also a preventative medicine available, a monoclonal antibody treatment, and this is for infants, either whose mothers weren't vaccinated during pregnancy, or who are at increased risk of severe RSV. Now, I think this particular treatment was rolled out in a few states in Australia in 2024 but as of this year is more widely recommended. Can you tell us about how this treatment works?
Jim Buttery: So this is a monoclonal antibody that is made in high concentrations to be given to the baby, and then they've modified the antibody so that it provides long-lasting protection for more than five months, so that the babies are protected all the way through their first RSV season, if you like. Because like many infections like flu, RSV has its greatest activity in most places in Australia during the cold months.
Olivia Willis: So, given the rollout now of the antibody treatment nationally, as well as, of course, the introduction of the vaccine earlier this year, what impact is this having on rates of RSV infection and also hospitalisations?
Jim Buttery: We already know from Western Australia that there's been a high level of protection from the nirsevimab program, and we can observe from our overall rates of admission of young children to hospital, there does appear to be, at least in Victoria where we have access to the data, evidence of early protection in young children against admissions to hospital with the conditions that are typically caused by RSV, the lung infections like pneumonia and bronchiolitis in particular.
Olivia Willis: And is it possible to attribute that to increase rates of vaccination, or is that about the antibody treatment or a combination of both?
Jim Buttery: At the moment, all we can say is that it's been a good year, and we'll soon be able to directly tie that to receipt of either maternal vaccine or nirsevimab. The rates of RSV infections vary a little bit from year to year, but 2025 is the best year we've seen for a long time, which is very encouraging.
Olivia Willis: And so when it comes to RSV research, what's next in this space?
Jim Buttery: It's a really active space. What we're using is some massive datasets, both in Victoria and also our collaborators in South Africa, to explore whether RSV infection itself might potentially increase the risk of prematurity, and there are some early findings suggesting that it may contribute from natural infection towards prematurity as well. We're also using the Gen V cohort, the statewide cohort of children born over a two-year period in Victoria to reinforce vaccine safety for antenatal vaccines delivered during pregnancy, and to confirm the development and allergic outcomes of children born to those mums, compared to mums who weren't vaccinated.
Olivia Willis: And just to clarify, what's the thinking around looking at allergic reactions?
Jim Buttery: The background to it is that one of the most common concerns that anti-vaccine groups raised around vaccination in pregnancy is that the vaccination may increase the risk of allergies. And so we're taking advantage of the Gen V cohort to examine that, using very large numbers of children to detail the rate of allergy so that we can demonstrate, as a number of studies have done that have been smaller in the past, that there's no increased risk of allergic outcomes in babies whose mums have received vaccines during pregnancy.
Olivia Willis: Professor Jim Buttery, head of Epidemiology Informatics at the Murdoch Children's Research Institute, and an infectious diseases physician at the Royal Children's Hospital in Melbourne.
Norman Swan: And Victoria is expanding the availability of the vaccine.
Olivia Willis: Yeah, just this week the Victorian government rolled out RSV vaccines to residents aged 60 and over in public aged care services and Aboriginal community controlled aged care services. And interestingly the technical advisory group, which advises the federal government on vaccines, they actually recommend that in Australia all adults over the age of 75 and people over 60 with increased risks of severe RSV, they recommend that those groups are vaccinated. But vaccines at the moment are only subsidised for pregnant women, so even though these groups are recommended to receive RSV vaccines, they have to pay for it out of their own pocket.
Norman Swan: And the College of GPs is calling on government to expand the eligibility to these groups.