RSV circulating variants

The Respiratory Syncytial virus (RSV) Fusion (F) protein is the main target of current vaccines and antibody-based therapies. It is highly conserved across both RSV-A and RSV-B subtypes. This page summarizes the genetic variants known to confer resistance to monoclonal antibodies. Last updated 02/December/2025.

RSV fusion protein

RSV F protein contains five antigenic sites, the most significant being Site 0 and Site II, which are bound respectively by Nirsevimab and Palivizumab antibodies .

PDBe Molstar viewer documentation (external)

Reference sequences (from Nextclade):

RSV-A isolate hRSV/A/England/397/2017 PP109421, Fusion protein fasta
RSV-B isolate hRSV/B/Australia/VIC-RCH056/2019 OP975389, Fusion protein fasta

RSV F protein: Click to highlight 3D structure regions of interest

site 0
- nirsevimab binding
site I
site II
- palivizumab binding
site III
site IV
site V
Glycosylations
(sites 116,120,and 126 not displayed because part of cleaved off p27 peptide)

Nirsevimab resistance sites

RSV-A Nirsevimab resistance N67I +N208Y
RSV-A Nirsevimab possible resistance K68E
RSV-B Nirsevimab resistance I64T/M +K68E
RSV-B Nirsevimab resistance K68N/E/Q
RSV-B Nirsevimab resistance N201S/T
RSV-B Nirsevimab resistance N208S/D

Palivizumab resistance sites

RSV-A Palivizumab resistance K272M/T
RSV-A Palivizumab resistance N262DPMID: 28867684
RSV-A possible Palivizumab resistance N268IPMID: 15767398
RSV-A Palivizumab resistance S275F
RSV-B Palivizumab resistance K272N/Q

RSV resistance mutations

Text file of mutations

Antibody	binding epitope	site	subtype	Variants	Effect	Reference	Pathoplexus sequences
Nirsevimab (MEDI8897) Beyfortus	Site 0 65,68,200,201,202,208,209	64	RSV-B	I64T	Resistance		I64T
		64	RSV-B	I64M + K65E	Resistance		I64M, K65E
		65	RSV-B	K65Q/T	Partial resistance		K65Q, K65T
		65	RSV-B	K65Q + S211N/D	Partial resistance		K65Q, S211N, S211D
		67	RSV-A	N67I +N208Y	Resistance		N67I N208Y
		68	RSV-A	K68E	Partial resistance		K68E
			RSV-B	K68E/Q	Resistance	,	K68E
			RSV-B	K68N	Partial resistance	,	K68N
		201	RSV-B	N201S/T	Resistance	,	N201S
		208	RSV-B	N208S/D	Resistance	PMC9752125,	N208S
Palivizumab Synagis	site II 262,272,275,276	262	RSV-A	N262Y	Resistance	PMC4004766	N262Y
		272	RSV-A	K272M/T	Resistance		K272M, K272T
			RSV-A	K272E/Q	Resistance	PMC4004766	K272E, K272Q
			RSV-B	K272N/Q	Resistance		K272N, K272Q
			RSV-B	K272R	Partial resistance		K272R
		275	RSV-A	S275F	Resistance		S275F

Other sources: Virus French resistance