Nirsevimab at a glance
Medicine class
Long-acting antiviral monoclonal antibody; it is not a vaccine.
Main role
Prevention of RSV lower respiratory tract disease in infants and vulnerable young children.
Administration
Intramuscular injection given by a trained healthcare professional, usually into the outer thigh.
NHS availability
Used selectively in secondary care for eligible premature or otherwise high-risk infants and young children.
What is Nirsevimab used for?
UK-licensed uses are:
Preventing RSV lower respiratory tract disease in neonates and infants during their first RSV season.
Preventing RSV lower respiratory tract disease in children up to 24 months old who remain vulnerable to severe disease during their second RSV season.
NHS access is more selective than the full licensed indication and follows national eligibility recommendations.
How does Nirsevimab work?
Nirsevimab binds to the prefusion form of the RSV fusion protein, blocking the membrane-fusion step needed for the virus to enter cells and spread. It supplies ready-made antibodies rather than stimulating the child to produce antibodies as a vaccine does.
Nirsevimab preparations and strengths
Injection
Route: Parenteral
Strengths: 50 mg, 100 mg
How to take Nirsevimab
Nirsevimab is administered by a trained healthcare professional and is not suitable for self-injection.
It is injected into a muscle, preferably the outer front part of the thigh.
The buttock is not routinely used because of the risk of sciatic nerve injury.
If given alongside injectable childhood vaccines, separate syringes and different injection sites must be used.
Food does not affect administration.
Nirsevimab side effects
Common or expected effects
- No adverse reactions are classified as common in the selected SmPC. Reported uncommon effects include rash, fever and injection-site pain, redness, swelling or hardness.
Get urgent medical advice
- Hypersensitivity reactions can occur. Urgent symptoms include difficulty breathing or swallowing, facial or throat swelling, collapse, or a severe widespread itchy or raised rash.
Nirsevimab in pregnancy
Pregnancy is marked as not applicable because nirsevimab is licensed for infants and young children, not as maternal immunisation. RSV vaccination during pregnancy is a separate UK programme.
Nirsevimab while breastfeeding
Lactation is marked as not applicable because nirsevimab is given to the child rather than the breastfeeding parent. Specialist advice is appropriate if use is considered outside its licensed paediatric population.
Nirsevimab interactions
Clinically important medicine interactions are not expected, but injection-related precautions still apply.
Routine childhood vaccines
They may be given at the same appointment, but must not be mixed with nirsevimab and should use separate syringes and injection sites.
Anticoagulants
They may increase bruising or bleeding from the intramuscular injection, so tell the clinical team beforehand.
Common questions about Nirsevimab
Answers are fully visible for fast scanning and source review.
Is nirsevimab a vaccine?
No. It is a monoclonal antibody that supplies ready-made RSV-specific antibodies rather than training the immune system in the same way as a vaccine.
What does nirsevimab protect children against?
It is intended to prevent lower respiratory tract disease caused by RSV, including serious bronchiolitis or pneumonia.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.