You may have heard respiratory syncytial virus (RSV) making the headlines many times over this year, with the introduction of two new vaccines and preventative antibodies in Australia. These are exciting developments, given the problems that RSV can cause in our babies and older adults in the community.
The information in this blog will focus on the maternity vaccine and preventative antibodies used in babies and young children.
What is RSV?
Respiratory syncytial virus, more commonly referred to as RSV, is a common virus which causes problems in the respiratory system. RSV is spread by droplets from coughing or sneezing from an infected person.
Most children have been exposed to RSV by the age of 2.
Peak months for RSV infection are between April to September (but are less seasonal in tropical regions of Australia)- but infections can occur all year round.
Antivirals have limited effectiveness in treating RSV, so the priority is in preventing the severity of infection in those who are considered at ‘high risk’ such as newborn babies, premature babies, older adults (>65 years), adults with chronic heart or lung disease and those from Aboriginal and Torres Strait Island backgrounds as well as those with ‘at-risk’ conditions.
What are the risks of RSV?
RSV is the most common cause of viral infections in the lungs, and can lead to pneumonia and bronchiolitis.
In Australia, there were 115,000 hospitalisations due to RSV between 2016 and 2019, and most occurred in children less than 5 years of age.
There are emerging studies that demonstrate that children who have significant RSV infection in their first two years of life are at increased risk of developing recurrent wheeze and potentially asthma.
What RSV vaccines are available?
In Australia, there are two new RSV vaccines.
One is for pregnant women to protect their newborn babies, the other is for older adults. These vaccines are designed to reduce the severity of RSV infection.
Both vaccines are intramuscular injections given at the start of the RSV season, where possible. The maternal vaccine needs to be given at least 2 weeks before a baby is born to be effective.
With current information, protection for both vaccines lasts 2 years. At this stage, no further recommendations have been made about booster doses.
Maternal vaccine- Abrysvo
In March 2024, Abrysvo was made available in Australia privately, meaning it incurs an out-of-pocket cost for those who choose to access it. From Winter next year (2025), this vaccine will be funded for all pregnant women.
Abrysvo is a protein vaccine (like Hepatitis B, HPV and pertussis), not a mRNA vaccine. It is also unadjuvanted, meaning additional substances have not been added to improve the immune response.
Abrysvo is recommended between 28 and 36 weeks of pregnancy. This helps the mother's immune system create antibodies against RSV, which are passed to the baby through the placenta. These antibodies protect the baby from RSV from birth until about six months of age. Women who are breastfeeding but not pregnant are not recommended to Abrysvo. Although there is no safety issue here, there is insufficient evidence to suggest that vaccination would protect a breastfeeding baby.
Vaccination is safe for the mother and baby, and it can be given with the pertussis (whooping cough), influenza, and COVID-19 vaccines.
Common side effects include:
injection site pain
fatigue
muscle pain
headache
Unlike the pertussis (whooping cough) vaccine, RSV vaccines are not routinely recommended for carers or those visiting newborns. However, depending on their age, they may be eligible for Arexvy (the RSV vaccine for older adults), for their own protection against RSV.
These vaccines are a significant step forward in reducing the impact of RSV, but for babies at higher risk, additional preventative measures such as preventative antibodies are also available.
What are preventative antibodies for RSV?
RSV preventative antibodies, also known as monoclonal antibodies, are man-made proteins that simulate antibodies produced by the immune system to fight RSV infection.
There are two preventative antibodies we use in Australia.
- Palivizumab (Synagis): Requires monthly injections during the five months of peak RSV season.
- Nirsevimab (Beyfortus): A single injection, Nirsevimab provides protection for approximately five months and can be safely administered alongside other age-appropriate vaccines without interaction concerns. Currently, it is only available in some states and territories, but this may change in 2025.
Preventative RSV antibodies are recommended for babies who:
Were not protected by the maternal vaccine (at least two weeks before birth)
Are at increased risk of severe disease, regardless of maternal vaccination status.
Have medical conditions that heighten the risk of severe RSV disease and are in their second RSV season, under the age of two.
Children with asthma or underlying medical conditions who are over 2 years of age, are not eligible for the preventative antibodies, because they will have already been exposed to RSV.
What else can you do to prevent RSV?
To help prevent RSV, you should follow all of the usual ‘cold and flu’ precautions, such as:
Hand Hygiene: Wash hands frequently with soap and water for at least 20 seconds, or use alcohol-based hand sanitiser when handwashing is not possible.
Avoiding Close Contact: Keep sick individuals away from vulnerable people, such as newborns and older adults, especially during peak RSV seasons.
Cleaning and Disinfection: Regularly clean and disinfect frequently touched objects and surfaces, such as doorknobs, toys, and mobile devices.
When you are unwell, you should:
Stay home to prevent the spreading of disease.
Stay away from vulnerable populations like newborn babies and older adults, as they are at higher risk
When coughing or sneezing, cover your mouth and nose with a tissue or your elbow. Dispose of tissues immediately.
In summary, RSV poses a significant risk to vulnerable populations, but advancements in vaccines and preventative antibodies are providing new opportunities to reduce its impact. Combined with everyday precautions like good hygiene and staying home when unwell, these tools empower us to better protect our loved ones, particularly babies and young children.
If you would like to read some specific information about the vaccine trials we have included them below.
Disclaimer:
This blog post was written by Dr Linny Kimly Phuong, a Paediatric Infectious Diseases Physician based in Melbourne, Australia. You may find her on her professional Instagram account @drlinnykp.
The information contained within this article was factually correct as at 28th November 2024.
This article is not a substitute for medical advice. Please speak with your healthcare professional for tailored advice and recommendations.
This article is not a paid endorsement by any mentioned pharmaceutical companies.
Trial Information
Maternal vaccine- Abrysvo
The main clinical trial (MATISSE study) for this vaccine was conducted in 18 countries, across 4 RSV seasons, in 7,392 healthy women who were between 24-36 weeks pregnant (with single baby in utero). Expectant mothers received either the vaccine or placebo.
The clinical trial did not include any ‘high risk’ pregnancies- which includes but is not limited to pregnancy resulting from IVF, women with a pre-pregnancy BMI>40kg/m2, those with pregnancy complications including preeclampsia, uncontrolled high blood pressure, placental abnormalities and untreated metabolic conditions.
In babies, Abrysvo reduces:
the risk of severe RSV disease: by 82% at 3 months and 70% at 6 months of age;
any medically attended RSV-associated lower respiratory tract illness: by 57% at 3 months, 51% at 6 months of age;
RSV-associated hospitalisation by 57% at 6 months,
Nirsevimab
(International, multi-centre trial)
1,453 infants across 164 sites in 23 countries received either nirsevimab or placebo two months before the beginning of the RSV season.
Participating infants were:
pre-term babies born between 29 to 34+6 weeks of gestation AND
young children 1 year or younger entering their first RSV season
Niservimab reduced medically attended RSV-associated lower respiratory tract infection by 70% (3 months after the dose). Hospitalisation was also 78% lower in the nirsevimab group compared to the placebo.
Adverse events were similar in both treatment and placebo groups. Serious adverse events were not sig were no statistically significant
The most common side effects were injection site reactions and rash.
MELODY trial
(term and late pre-terms)
3,012 infants, at least 35 weeks gestation
Effectiveness (150 days after administration) of nirsevimab against:
Hospitalisation for RSV associated lower respiratory tract infection was 77%
Very severe RSV infection was 79%
References:
- Australian Technical Advisory Group on Immunisation (ATAGI)- Australian Government Department of Health and Aged Care. Australian Immunisation Handbook, Canberra, Australia
- Domachowske J, Madhi SA, Simões EAF, et al. Safety of Nirsevimab for RSV in Infants with Heart or Lung Disease or Prematurity. New England Journal of Medicine. 2022;386(9):892-4
- Griffin MP, Yuan Y, Takas T, et al. Single-Dose Nirsevimab for Prevention of RSV in Preterm Infants. New England Journal of Medicine. 2020;383(5):415-25.
- Hall CB, Weinberg GA, Iwane MK, et al. The burden of respiratory syncytial virus infection in young children. N Engl J Med. 2009;360(6):588-98
- Kampmann B, Madhi SA, Munjal I, et al. Bivalent Prefusion F Vaccine in Pregnancy to Prevent RSV Illness in Infants. New England Journal of Medicine. 2023;388(16):1451-64.
- Li Y, Wang X, Blau DM, et al. Global, regional, and national disease burden estimates of acute lower respiratory infections due to respiratory syncytial virus in children younger than 5 years in 2019: a systematic analysis. Lancet. 2022;399(10340):2047-64.
- Madhi SA, Ceballos A, Cousin L, et al. Population Attributable Risk of Wheeze in 2-<6-Year-old Children, Following a Respiratory Syncytial Virus Lower Respiratory Tract Infection in The First 2 Years of Life. Pediatr Infect Dis J. 2024
- Muller WJ, Madhi SA, Nuñez BS, et al. Nirsevimab for Prevention of RSV in Term and Late-Preterm Infants. New England Journal of Medicine. 2023;388(16):1533-4.
- Royal Australian & New Zealand College of Obstetricians and Gynaecologists, Pre-pregnancy and pregnancy-related vaccinations, last updated Oct 2024 https://ranzcog.edu.au/wp-content/uploads/Pre-Pregnancy-and-Pregnancy-Related-Vaccinations.pdf
- Saravanos GL, Sheel M, Homaira N, et al. Respiratory syncytial virus-associated hospitalisations in Australia, 2006-2015. Med J Aust. 2019;210(10):447-53.
- Shi T, McAllister DA, O'Brien KL, et al. Global, regional, and national disease burden estimates of acute lower respiratory infections due to respiratory syncytial virus in young children in 2015: a systematic review and modelling study. Lancet. 2017;390(10098):946-58
