When your baby falls ill, even a mild cough or fever can feel worrying. Recently, public health campaigns in Singapore have been drawing attention to RSV, or respiratory syncytial virus, and the need to protect infants from this.

RSV is a highly contagious virus that usually starts with what looks like a common cold — a runny nose, congestion, sore throat, or a mild fever. Unlike the flu, where symptoms often appear suddenly, RSV tends to creep in gradually over a few days. 

While most children recover without major issues, RSV can be more serious in certain groups, such as babies under six months, those born prematurely, or those with underlying heart or lung conditions. This can lead to bronchiolitis (inflammation of the small airways in the lungs) or pneumonia (infection of the lungs), which can require hospital care.

Paediatricians advise parents to watch for red flags such as rapid or shallow breathing, poor feeding, unusual tiredness, or pauses in breathing. These are signs that your child may require urgent medical attention.

Globally, around two in three babies will catch RSV before their first birthday, and it remains the leading cause of lower respiratory tract disease in infants. In Singapore, about 1,800 children under 29 months are hospitalised due to RSV-related illnesses each year.

How to prevent RSV in babies?

Previously, protecting babies from RSV meant avoiding crowded places, practising good hand hygiene, and keeping a close eye on symptoms. There was no way to provide infants with direct protection against the virus.

Now, there is a new option. 

Beyfortus^® (nirsevimab)* was recently approved by Singapore’s Health Sciences Authority to protect all infants against RSV. It is given as a single injection. 

It is suitable for newborns and infants from birth, as well as for children up to 24 months of age who remain at risk of severe RSV.

* Beyfortus is the brand name, while nirsevimab is the active ingredient that helps protect infants against RSV.

Is Beyfortus a vaccine?

No, Beyfortus is not a vaccine. 

Vaccines train the body to build its own defences over time. Beyfortus instead provides antibodies — proteins that act like the body’s “defence soldiers” against infection. 

Because the antibodies are given directly, babies gain protection straight after the injection. One dose lasts for at least five months, long enough to cover a typical RSV season in Singapore (May to September).

How has Beyfortus been tested?

Beyfortus has been studied in several international trials, and here are the key findings:

• HARMONIE: This study followed more than 8,000 infants across Europe. It showed that babies who received Beyfortus had an 82.7% lower risk of being hospitalised for RSV in the six months after the injection, compared with those who did not receive it. 
• MELODY: This study involved healthy full-term and late preterm babies. It showed that Beyfortus lowered the risk of RSV lower respiratory tract disease (LRTD) requiring medical care by 74.5%.
• Phase 2b study: A ‘Phase 2b’ study is an early but important trial that tests how well a treatment works in a larger group, before moving on to bigger confirmatory trials. This study focused on healthy preterm babies, who are more vulnerable to severe RSV. It showed that Beyfortus reduced the risk of RSV lower respiratory tract disease (LRTD) needing medical care by 70.1%, and reduced RSV-related hospitalisations by 78.4%.

Locally, a panel of paediatric experts reviewed the evidence on RSV and nirsevimab, the antibody used in Beyfortus. The panel highlighted that RSV is a major cause of hospitalisation in young children, especially those under two, and agreed that a single dose of nirsevimab could be offered to all infants as a way to reduce this burden.

Is Beyfortus safe?

In clinical trials, the most common reactions after the injection were mild, such as a rash or swelling at the injection site. Overall, the rate of side effects was similar between babies who received Beyfortus and those who were given a placebo.

One important safety study, called MEDLEY, looked specifically at preterm babies and those with lung or heart conditions. It compared Beyfortus with palivizumab, an older antibody injection that has been used in Singapore for years but is only given to a small number of very high-risk infants. The results showed that Beyfortus had a similar safety profile to palivizumab, with no new safety concerns. 

In all, the data so far suggests that Beyfortus is well tolerated. Apart from Singapore, Beyfortus has also been approved in the European Union, the US, China, and Japan.

Want to know more about RSV protection? Check with your paediatrician or family doctor, who will have the latest guidance.