Why is my baby being offered an RSV immunisation nirsevimab?
Published 19 August 2025
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What is RSV?
Respiratory syncytial virus (RSV) is a common infection that affects the lungs. When small children catch RSV, it makes it hard for them to breathe and can lead to bronchiolitis or pneumonia. Around 20,000 infants are admitted to hospital with RSV each year in England.
RSV is highly infectious and spreads easily, particularly among children. RSV infections can happen all year round but most occur in the winter.
The best way to protect your baby against RSV infection is through immunisation.
Which immunisation is my child being offered?
Your child is being offered nirsevimab, a type of immunisation that contains antibodies. These antibodies will help their immune system to fight RSV infection. This extra protection is needed because your child is at higher risk from RSV than other children. This is either because they were born early or because they have certain medical conditions.
Why does my child need this immunisation?
Most babies will get protection against RSV from their mother, due to antibodies that are boosted by being vaccinated against RSV during pregnancy. If your baby is born early, then there may not be time for the mother to be vaccinated or to respond well to the vaccine. Other babies may require extra protection because they have certain conditions that affect their heart, breathing or their immune system. This includes children up to 2 years old with severe combined immunodeficiency (SCID). These babies are recommended to receive nirsevimab to give them extra protection over the time when they are most at risk of severe RSV infection. Most babies will only need this protection over their first winter. As they get older, they are better able to fight the infection.
Does my baby need nirsevimab if I had an RSV vaccine when I was pregnant?
The doctor at the hospital will recommend if your baby requires nirsevimab to give them extra protection against RSV, even if the mother had the RSV vaccine during pregnancy. Babies that are born early (before 32 weeks) and those that have medical conditions that put them at high risk for severe RSV can safely have nirsevimab even if their mum had the RSV vaccine.
Will nirsevimab completely protect my baby from RSV?
No immunisation gives complete protection but nirsevimab reduces the risk of needing hospital admission for RSV by at least 80%. This level of protection has been seen in clinical trials and in immunisation programmes in different countries. This protection lasts for at least five to six months.
Are there any side effects?
Some children will have side effects after an injection but these are uncommon (less than 1 in 100 children) and usually mild. These may include:
- rash
- redness, swelling or soreness where they had the injection
- high temperature, also called a fever
The brand name of nirsevimab is Beyfortus. You can read more about it in the manufacturer’s patient information leaflet (PIL).
Reporting of side effects
If your child gets any side effects, talk to your child’s healthcare professional. This includes any possible side effects not listed in this leaflet.
You can report suspected side effects of vaccines and medicines through the Yellow Card Scheme:
- online at Yellow Card Scheme
- by downloading and using the Yellow Card app on Apple or Android
- by calling the Yellow Card scheme on 0800 731 6789 (9am to 5pm)
By reporting side effects, you can help provide more information on the safety of this medicine.
The symptoms of RSV
The symptoms of RSV bronchiolitis can include:
- runny or blocked nose
- breathing is difficult, fast or noisy (wheezing)
- difficulty feeding
- cough
- fever
- unsettled or difficult to comfort
- tiredness or lethargy
RSV can also cause other conditions in young children such as a barking cough (croup) and a painful infection inside the ear (otitis media). Ask for an urgent GP appointment or get help from NHS 111 if:
- your child is unwell and it’s getting worse
- your child is feeding or eating much less than normal
- your child has had a dry nappy for 12 hours or more, or shows other signs of dehydration
- your baby is under 3 months and has a temperature of 38 degrees Celsius (°C) or is older than 3 months and has a temperature of 39°C or higher
Call 999 or go to A&E
If your child seems seriously unwell, trust your own judgement.
You should act if:
- your child is having difficulty breathing
- you may notice grunting noises or their chest and tummy wall being sucked in between or just under their ribs
- there are pauses when your child breathes
- your child’s skin, tongue or lips are blue
- your child is floppy and will not wake up or stay awake