Introduction of Clesrovimab (Enflonsia) as an additional product for RSV passive immunisation in at-risk infants (WHC/2026/029)

Status:

Action

Catergory: 

Public Health

Title: 

Introduction of Clesrovimab (Enflonsia) as an additional product for passive immunisation against Respiratory Syncytial Virus (RSV) in at risk infants for upcoming 2026 to 2027 RSV Season

Date of Expiry: 

Not applicable

For Action by: 

• Chief Executives, Health Boards and Trusts
• Immunisation Leads, Health Boards and Trusts 
• Immunisation Coordinators, Health Boards
• Vaccination Operational Leads, Health Boards and Trusts
• Medical Directors, Health Boards and Trusts
• Directors of Primary Care, Health Boards and Trusts
• Nurse Executive Directors, Health Boards and Trusts
• Chief Pharmacists, Health Boards and Trusts
• Directors of Public Health, Health Boards and Trusts
• Executive Director of Public Health, Public Health Wales
• Head Vaccine Preventable Disease Programme, Public Health Wales
• Director of Vaccine Delivery, Vaccination Programme Wales, NHS Executive.
• Community Paediatricians, Health Boards
• Heads of Midwifery, Health boards and Trusts.
• Midwifery teams, Health Boards
• Secondary Care Paediatricians, Health Boards 
• Consultant Virologists, Health Boards
• Health Protection teams, Health Boards
• General Practitioner Committee, Wales
• General practitioners
• Digital Health and Care Wales.

Action required by: 

July 2026

Sender:  

Professor Isabel Oliver, Chief Medical Officer

Health, Social Care and Early Years Group Welsh Government Contact(s):

Vaccination Division, 
Welsh Government, 
Cathays Park, 
Cardiff CF10 3NQ 
Email: wg.vaccinationsprogrammeteam@gov.wales 

Enclosures: 

None

I write to advise that an additional product is now available for the RSV selective immunisation programme for at-risk infants, previously referenced in WHC/2025/029. The new product is Clesrovimab (Enflonsia) and the Joint Committee on Vaccination and Immunisation (JCVI) has advised this product is equivalent to Nirsevimab, which was introduced last year.

Globally, RSV infects up to 90% of children within the first two years of life and frequently reinfects older children and adults. Infants under one year of age and the elderly are at the greatest risk of hospitalisation with more severe RSV. The clinical significance of RSV in infants is that it can cause bronchiolitis, which leads to the inflammation of the small airways and significant breathing difficulties. 

Last year I wrote to you advising of an expansion of eligibility and those cohorts are confirmed again as:

• preterm infants born less than 32 weeks who are entering their first RSV season
• the existing eligible groups from the previous iteration of this programme as indicated in the Green book

Planning for these changes should commence immediately and supplies should now be sourced for the incoming RSV season. Administration should commence  in line with the guidance in the Green book.

Clesrovimab and Nirsevimab will both be available to purchase through the NHS Wales Framework agreement with ordering information available from NWSSP procurement services.

Funding adjustments have been confirmed to health board finance teams. Further changes to this programme will be considered in the future, based on emergence of new products or additional information that may become available. 

The RSV chapter of the Green book, which contains information about the use of Nirsevimab and the new product, Clesrovimab, is expected to have further revisions, so healthcare professionals should continue to consult this document for the latest advice.

Programme support will be available through the National Strategic Clinical Network for Maternity and Neonatal Services team within NHS Wales Performance and Improvement.

The Royal College of Paediatrics and Child Health in partnership with UK Health Security Agency conducted a webinar to support the introduction of the new product. 

This is available to watch here: RCPCH Grand Round: Respiratory syncytial virus (RSV) immunisation update 2026 - RCPCH Learning

SNOMED procedure code advised for the recording of the monoclonal antibody immunisation:  

• Programme: NHS RSV Passive Immunisation Programme
• Procedure name: Administration of Respiratory Syncytial virus immune globulin, human (procedure)
• SNOMED procedure code: 117089007

Descriptors and SNOMED codes for the RSV vaccination Abrysvo used for the NHS maternal and older adult RSV programmes MUST NOT be used to record the monoclonal antibody immunisation Nirsevimab.   

It is important that administration of Clesrovimab/Nirsevimab is NOT recorded as ‘RSV vaccination’ or abbreviated to ‘RSV immunisation’ in infant records where it could be mistakenly interpreted as the RSV vaccine Abrysvo.

I would like to take this opportunity to thank everyone involved in this important programme in Wales.  New RSV vaccines and monoclonal antibodies are protecting more babies and older adults from becoming seriously ill. The introduction of another product helps us to continue to protect this vulnerable cohort. I am extremely grateful for the work and commitment shown to the programme. 

Yours sincerely,

Professor Isabel Oliver

Chief Medical Officer