Respiratory syncytial virus (RSV) is a common respiratory infection that poses the greatest threat to infants under 6 months old and adults over 60, with hospitalization rates dramatically higher in these age groups compared to healthy children and younger adults. Nearly all children experience at least one RSV infection by age two, but severe disease requiring hospitalization concentrates in specific vulnerable populations. Australia's new National RSV Mother and Infant Protection Program, launched in February 2025, is now providing free vaccines and monoclonal antibodies to protect these high-risk groups .

Who Is Most Vulnerable to Severe RSV Disease?

RSV affects people of all ages, but the burden of severe disease falls unevenly across the lifespan. Between 2016 and 2019, Australia recorded more than 115,000 hospitalizations with an RSV diagnosis, with approximately 75% occurring in children under 5 years old . However, the hospitalization rate tells a more nuanced story when broken down by age.

For infants under 6 months, the annual RSV hospitalization rate was approximately 3,100 per 100,000 population during that period, with the highest rates in infants aged 0 to 2 months at approximately 4,000 per 100,000 population . This means that in this youngest age group, severe RSV disease is far more common than in older infants and young children. The hospitalization rate then declines sharply as children age through early childhood, only to increase again in late adulthood, creating a distinctive U-shaped risk curve across the lifespan.

Certain infants and young children face even higher risk than their healthy peers. These include:

• Age and Development: Infants under 6 months, particularly those under 3 months old, experience the highest hospitalization rates due to their immature immune systems and smaller airways.
• Underlying Medical Conditions: Young children aged 2 years and under with chronic lung disease or congenital heart disease face significantly elevated risk of severe RSV disease.
• Prematurity: Infants and young children aged 2 years and under who were born prematurely are at greater risk of requiring hospitalization.

In older adults, hospitalization rates increase again, particularly in those aged 75 and over, Aboriginal and Torres Strait Islander people aged 60 and over, and adults aged 60 and over with underlying medical conditions such as chronic lung disease or heart disease .

What New Immune Protection Options Are Now Available?

Australia has introduced multiple immunization strategies to protect vulnerable populations from severe RSV disease. The approach differs based on age and risk factors, reflecting how the immune system's ability to respond to RSV protection varies across the lifespan.

For pregnant women and newborns, the Abrysvo vaccine offers a novel form of protection. A single dose of Abrysvo is recommended and funded through Australia's National Immunisation Program for pregnant women of all ages, administered between 28 weeks gestation and delivery . This vaccine works through passive immunization, meaning the mother's immune system produces antibodies that transfer to the developing fetus, providing the newborn with immediate protection during the most vulnerable first months of life.

For infants too young to mount their own immune response, a long-acting monoclonal antibody called Beyfortus (nirsevimab) is available for free to eligible infants through state and territory-funded programs . Unlike vaccines, which stimulate the body's own immune system to produce antibodies, monoclonal antibodies are laboratory-made proteins that directly provide immune protection. This approach bypasses the need for the infant's immature immune system to generate its own response.

Older adults have access to RSV vaccines designed to activate their immune systems. RSV immunization with Arexvy is currently funded for Victorian residents aged 60 and over in public and Aboriginal community-controlled aged care services . A single dose of RSV vaccine (either Arexvy or Abrysvo) is recommended for people aged 75 and over, Aboriginal and Torres Strait Islander people aged 60 and over, and adults aged 60 and over with conditions that increase their risk of severe RSV disease .

How to Protect Your Family From RSV Across Different Life Stages

RSV protection strategies depend on age, health status, and access to funded programs. Here are the key steps families should consider:

• Pregnant Women: Discuss the Abrysvo vaccine with your healthcare provider at your 28-week antenatal visit to ensure your newborn receives passive immunity during the critical first months of life.
• Newborns and Young Infants: Ask your pediatrician whether your infant is eligible for Beyfortus (nirsevimab), particularly if your baby was born prematurely or has underlying medical conditions that increase RSV risk.
• Older Adults and Those with Chronic Conditions: Consult your doctor about RSV vaccination if you are 60 or older, have chronic lung or heart disease, or are Aboriginal or Torres Strait Islander, as these groups face significantly elevated hospitalization risk.
• Caregivers of High-Risk Infants: While parents and caregivers are not currently recommended to receive RSV vaccines to protect infants, maintaining good respiratory hygiene and staying home when sick remains important to reduce transmission risk.

When Does RSV Season Peak, and Why Does It Matter?

RSV seasonality varies by geography and climate. In most temperate regions of Australia, seasonal outbreaks occur during autumn and winter, typically between April and September, with peaks during June and July, often preceding the influenza season . In tropical regions, RSV seasonality is less pronounced and may coincide with rainy seasons .

Understanding RSV seasonality matters because it helps families and healthcare providers anticipate when vulnerable populations face the greatest risk. Infants born during or just before RSV season face higher hospitalization risk, making prenatal vaccination particularly valuable for pregnant women expecting delivery during winter months. Older adults should discuss vaccination timing with their healthcare providers to ensure protection is in place before the season begins.

RSV can occur year-round in Australia, but hospitalization rates are more common during winter months . This seasonal pattern underscores why timing of immunization matters for maximizing protection when risk is highest.

What Makes RSV Different From Other Respiratory Viruses?

RSV causes a range of respiratory illnesses, from mild upper respiratory colds to severe lower respiratory conditions. Symptoms include runny nose, cough, fever, and wheezing or difficulty breathing, including exacerbations of underlying lung disease such as asthma . The virus spreads through droplets from an infected person's cough or sneeze, which can be inhaled by others or land on surfaces where the virus can survive for several hours .

What distinguishes RSV from many other respiratory viruses is the stark difference in disease severity between age groups. While most healthy children and adults experience only mild symptoms, the very young and the elderly face disproportionate risk of severe disease requiring hospitalization. This age-related vulnerability pattern has driven the development of age-specific immunization strategies rather than a one-size-fits-all vaccine approach.

The fact that nearly all children experience at least one RSV infection within the first two years of life means that RSV is essentially universal in childhood. The challenge for public health is not preventing infection entirely, but rather preventing the severe complications that occur in vulnerable populations. This is why the new immunization programs focus specifically on protecting infants during their most vulnerable months and older adults whose immune systems may struggle to mount an effective response to infection.