Document text
Effectiveness and impact of RSV
prevention products in infants during
the 2024 –2025 RSV season
Coronavirus and Other Respiratory Viruses Division
June 25, 2025National Center for Immunization and Respiratory Diseases
Product Effectiveness (PE)
•Summary of CDC systems used toevaluate PE
•Effectiveness of nirsevimab and maternal RSV
vaccine during the 2024 –2025 RSV season in
the U.S.
RSV Hospitalization Rates and Product Impact
•Summary of CDC systems used for monitoring
RSV hospitalization rates
•Impact of nirsevimab and maternal RSV
vaccine during the 2024 –2025 RSV season in
the U.S.Agenda
2
Product effectiveness
methods and CDC
systems used for
evaluation
3
Observational VE studies Methods1
Virtual SARS -CoV-2, Influenza,
and Other respiratory viruses
Network (VISION) Test-negative
design2,3,4
New Vaccine Surveillance
Network (NVSN)
Overcoming Network
(Overcoming)Matched Case -
Control5Study designs for observational PE studies
References for study design methods with relevant examples
1Roper L, et. al. A framework for monitoring RSV prevention product effectiveness in the United States. Vaccine 2025;45:126633
2 Chua H, et. al. The Use of Test -negative Controls to Monitor Vaccine Effectiveness: A Systematic Review of Methodology. Epidemiology 2020;31:43 –64.
3 Moline HL, et al. Respiratory Syncytial Virus Disease Burden and Nirsevimab Effectiveness in Young Children From 2023 -2024.. JAMA Pediatr 2025;179:179 -187.
4 Payne AB, et. al. Respiratory syncytial virus (RSV) vaccine effectiveness against RSV -associated hospitalisations and emergency department encounters among adults aged 60 years and older in the USA, October, 2023, to March, 2024: a test -
negative design analysis. Lancet 2024;404:1547 -1559.
5 Zambrano LD, et. al. Durability of Original Monovalent mRNA Vaccine Effectiveness Against COVID -19 Omicron -Associated Hospitaliz ation in Children and Adolescents - United States, 2021 -2023. MMWR 2024;73:330 -338Effectiveness = 1 – (odds ratio) x 100% Odds ratio = 𝑂𝑑𝑑𝑠 𝑜𝑓 𝑖𝑚𝑚𝑢𝑛𝑖𝑧𝑎𝑡𝑖𝑜𝑛 𝑐𝑎𝑠𝑒𝑠
𝑂𝑑𝑑𝑠 𝑜𝑓 𝑖𝑚𝑚𝑢𝑛𝑖𝑧𝑎𝑡𝑖𝑜𝑛 𝑐𝑜𝑛𝑡𝑟𝑜𝑙𝑠
4Persons who seek care for
RSV-like illness during
RSV seasonCases
Test positive for
RSVImmunized
Unimmunized
Controls
Test negative for
RSVImmunized
Unimmunized
CDC networks used to assess RSV product effectiveness
in infants and children
VISION
Multi -site network of electronic
health records (EHRs)
160 emergency department (ED)
and 131 hospitals in 6 states
Children visiting a participating ED
or hospital with RSV -like illness are
eligible for inclusionNVSN
Active surveillance for acute
respiratory illness (ARI) in children
7 academic pediatric health
systems in 7 states
Children hospitalized or visiting the
ED for ARI are eligible for
enrollmentOvercoming
Active surveillance for pediatric RSV
with case -control design
26 pediatric intensive care units
(ICUs) in 23 states
Children in a participating ICU with
ARI are eligible for inclusion.
5VISION: https://www.cdc.gov/flu -vaccines -work/php/vaccine -effectiveness/vision -network.html ; NVSN: https://www.cdc.gov/nvsn/php/about/index.html ; Overcoming: https://www.palisi.org/overcomecovid
;
Summary of CDC networks used to assess RSV product
effectiveness in children
VISION NVSN Overcoming
Infant and maternal
immunization dataElectronic health records, state
and city registries, and claims
data (subset of sites)Electronic health records, state
registries, out -of-network
provider records, parent reportElectronic health records,
state registries, provider
records, parent report
Analytic study period October 2024 –March 2025 October 2024 –March 2025 December 2024 –April 2025
Cases RSV-like illness (RLI) with
clinical positive RSV antigen or
nucleic acid amplification test
(NAAT)Acute respiratory illness (ARI)
with RSV detected on
systematic NAAT testingARI with clinical positive
RSV antigen or NAAT
Controls RSV-like illness with negative
RSV NAATAcute respiratory illness (ARI)
with no RSV detected on
systematic NAAT testingARI with negative NAAT;
Case -matched on site, age,
and date of hospitalization
6
Summary of VISION, NVSN, and Overcoming analytic
methods used to assess product effectiveness in children
VISION NVSN Overcoming
Nirsevimab
analytic populationInfants <8 months as of October 1, 2024, or born after October 1, 2024 with no maternal RSV
vaccination receipt
Maternal vaccine
analytic populationInfants born on or after
September 14, 2024 who did not
receive nirsevimabInfants <6 months of age during
the study period who did not
receive nirsevimabNot assessed
Analysis Multivariable logistic regression
models, adjusting for site, age in
months, calendar date, race and
ethnicity, and sex.
Models adjusting for underlying
medical conditions did not
meaningfully change estimates.Multivariable logistic regression
models, adjusting for site, age in
months, and month of enrollment.
Nirsevimab analysis adjusted for
presence of ≥1 high -risk medical
condition for severe RSV
disease; maternal RSV analysis
adjusted for race/ethnicity and
insurance status.Multivariable logistic
regression models, adjusting
for site, age in months,
timing of enrollment,
presence of ≥1 underlying
medical condition, and social
vulnerability index.
Outcomes assessed Hospitalization, emergency
department (ED) visit, intensive
care unit (ICU) admissionHospitalization, ED visit, ICU
admissionICU admission
7
Nirsevimab
effectiveness
during the
2024–2025
RSV season in
the United States
8
Nirsevimab product effectiveness (PE) against RSV -associated emergency department
(ED) visits among infants in their first RSV season, VISION & NVSN, 2024 –2025
*VISION analysis included children who received nirsevimab ≥7 days prior to encounter.
†Product effectiveness (PE) calculated as (1 -adjusted odds ratio)*100, with adjusted odds ratio estimated using multivariable log istic regression model, adjusting for site, age in months, calendar
date, race and ethnicity, and sex.
‡NVSN analysis included children who received nirsevimab ≥7 days prior to symptom onset.
§Product effectiveness (PE) calculated as (1 -adjusted odds ratio)*100, with adjusted odds ratio estimated using multivariable log istic regression model, adjusting for site, age in months, month of
enrollment, and presence of >1 high-risk medical condition for severe RSV disease.
IQR: Interquartile Range | CI: Confidence IntervalNirsevimab was effective against RSV -associated ED visits.SYSTEM
Nirsevimab StatusRSV-positive
encounters
N (Col %)RSV-negative
encounters
N (Col %)Median days
since dose
(IQR)Adjusted
PE (95% CI)
VISION1225 2833
No nirsevimab doses966 (79) 1799 (64)Not Applicable Reference
Nirsevimab, ≥7 days prior*259 (21) 1034 (36) 68 (37 -102) 63 (56 -69)†
NVSN 107 381
No nirsevimab doses92 (86) 214 (56)Not Applicable Reference
Nirsevimab, ≥7 days prior‡15 (14) 167 (44) 68 (41 -103) 76 (55 -87)§
0 50 100
Product Effectiveness (%)
9
Nirsevimab product effectiveness (PE) against RSV -associated hospitalization
among infants in their first RSV season, VISION & NVSN, 2024 –2025
SYSTEM
Nirsevimab StatusRSV-positive
encounters
N (Col %)RSV-negative
encounters
N (Col %)Median days
since dose
(IQR)Adjusted
PE (95% CI)
VISION286 318
No nirsevimab doses233 (81) 174 (55)Not Applicable Reference
Nirsevimab, ≥7 days prior*53 (19) 144 (45) 61 (27 -102) 79 (67 -87)†
NVSN 294 378
No nirsevimab doses263 (89) 229 (61)Not Applicable Reference
Nirsevimab, ≥7 days prior‡31 (11) 149 (39) 52 (27 -87) 82 (71 -88)§
Nirsevimab was effective against RSV -associated hospitalization.0 20 40 60 80 100
Product Effectiveness (%)
*VISION analysis included children who received nirsevimab ≥7 days prior to encounter.
†Product effectiveness (PE) calculated as (1 -adjusted odds ratio)*100, with adjusted odds ratio estimated using multivariable log istic regression model, adjusting for site, age in months, calendar
date, race and ethnicity, and sex.
‡NVSN analysis included children who received nirsevimab ≥7 days prior to symptom onset.
§Product effectiveness (PE) calculated as (1 -adjusted odds ratio)*100, with adjusted odds ratio estimated using multivariable log istic regression model, adjusting for site, age in months, month of
enrollment, and presence of >1 high-risk medical condition for severe RSV disease. 10
Nirsevimab product effectiveness (PE) against RSV -associated intensive care unit
(ICU) admission among infants in their first RSV season, VISION, NVSN &
Overcoming, 2024 –2025
SYSTEM
Nirsevimab StatusRSV-positive
encounters
N (Col %)RSV-negative
encounters
N (Col %)Median days
since dose
(IQR)Adjusted
PE (95% CI)
VISION 56 318
No nirsevimab doses 48 (86) 174 (55) Not Applicable Reference
Nirsevimab, ≥7 days prior*8 (14) 144 (45) 56 (25 -97) 82 (57 -93)†
NVSN 73 71
No nirsevimab doses 67 (92) 40 (56) Not Applicable Reference
Nirsevimab, ≥7 days prior‡6 (8) 31 (44) 52 (24 -84) 88 (63 -96)§
Overcoming 409 263
No nirsevimab doses 354 (87) 146 (56) Not Applicable Reference
Nirsevimab, ≥7 days prior* 55 (13) 117 (44) 50 (32 -86) 80 (73 -85)¶
Nirsevimab was effective against RSV -associated ICU admission.0 20 40 60 80 100
Product Effectiveness (%)
*Analysis included children who received nirsevimab ≥7 days prior to encounter.
†Product effectiveness (PE) calculated as (1 -adjusted odds ratio)*100, with adjusted odds ratio estimated using multivariable log istic regression model, adjusting for site, age in months, calendar
date, race and ethnicity, and sex. RSV -negative encounters were those among children hospitalized for RSV -like illness and not limited to children admitted to the ICU.
‡NVSN analysis included children who received nirsevimab ≥7 days prior to symptom onset.
§Product effectiveness (PE) calculated as (1 -adjusted odds ratio)*100, with adjusted odds ratio estimated using multivariable log istic regression model, adjusting for site, age in months, month of
enrollment, and presence of >1 high-risk medical condition for severe RSV disease.
¶Product effectiveness (PE) calculated as (1 -adjusted odds ratio)*100, with adjusted odds ratio estimated using multivariable log istic regression model, adjusting for age in months, timing of
admission, census region, presence of ≥1 underlying medical condition, and social vulnerability index. Hospital site included as a repeated measure. The analysis was not limited to matched pairs. 11
Maternal vaccine effectiveness during
the 2024–2025 RSV season in the
United States12
Maternal vaccine effectiveness (VE) against RSV -associated emergency
department (ED) visits among infants in their first RSV season, VISION, 2024 –2025
SYSTEM
Nirsevimab StatusRSV-
positive
encounters
N (Col %)RSV-negative
encounters
N (Col %)Median days
since birth (IQR)Median days
since dose
(IQR)Adjusted
VE (95% CI)
VISION333 660
No maternal
vaccine262 (79) 428 (65) Not Applicable Not Applicable Reference
Maternal vaccine* 71 (21) 232 (35) 53 (31 -90) 85 (65 -110) 54 (35 -67)†
Maternal RSV vaccine was effective against
RSV-associated ED visits in infants.0 20 40 60 80 100
Vaccine Effectiveness (%)
*VISION analysis included children who were born ≥14 days after maternal RSV vaccine dose.
†Vaccine effectiveness (VE) calculated as (1 -adjusted odds ratio)*100, with adjusted odds ratio estimated using multivariable log istic regression model, adjusting for site, age in months, calendar
date, race and ethnicity, and sex.
IQR: Interquartile Range | CI: Confidence Interval 13
SYSTEM
Vaccination StatusRSV-positive
encounters
N (Col %)RSV-negative
encounters
N (Col %)Median days since
birth (IQR)Median days
since dose
(IQR)Adjusted
VE (95% CI)
VISION 134 122
No maternal vaccine 109 (81) 77 (63) Not Applicable Not Applicable Reference
Maternal vaccine* 25 (19) 45 (37) 35 (17 -69) 73 (52 -111) 79 (55 -90)†
NVSN 108 213
No maternal vaccine 89 (82) 142 (67) Not Applicable Not Applicable Reference
Maternal vaccine‡19 (18) 71 (33) 32 (17 -58) 71 (50 -103) 70 (28 -88)§Maternal vaccine effectiveness (VE) against RSV -associated hospitalization
among infants in their first RSV season, VISION & NVSN, 2024 –2025
Maternal RSV vaccine was effective against RSV -associated hospitalization in infants.
*VISION analysis included children who were born ≥14 days after maternal RSV vaccine dose.
†Vaccine effectiveness (VE) calculated as (1 -adjusted odds ratio)*100, with adjusted odds ratio estimated using multivariable log istic regression model, adjusting for site, age in months, calendar date, race and ethnicity, and sex.
‡NVSN analysis included children who born ≥14 days after maternal RSV vaccine dose
§Vaccine effectiveness (VE) calculated as (1 -adjusted odds ratio)*100, with adjusted odds ratio estimated using multivariable log istic regression model, adjusting for site, age in months, month of enrollment, race/ethnicity, and health
insurance status . 140 20 40 60 80 100
Vaccine Effectivness (%)
•These surveillance systems have different enrollment methodologies and source populations and may
not be directly comparable.
•Residual confounding was possible
•Misclassification of RSV immunization status was possible, although all systems used multiple sources to
verify immunization status
•VISION:
-Cases may have sought care for something other than RSV
-All RSV testing was clinician -directed
-EHR data may not fully capture all underlying medical conditions, which may be associated with likelihood of
immunization and risk of severe RSV disease
•NVSN:
-May not be nationally representative
-Cases may have sought care for something other than RSV
•Overcoming Network:
-Enrollment began after the RSV season started
-All RSV testing was clinician -directed Limitations of product effectiveness analyses
15
Conclusions
16
Summary of RSV prevention product effectiveness (PE) among infants in
their first RSV season, 2024 –2025
Outcome Product CDC Network Product Efficacy* /Effectiveness (95% CI)
RSV-associated ED visitNirsevimabVISION 63 (56 -69)
NVSN 76 (55 -87)
Clinical Trial Not Applicable
Maternal VaccineVISION 54 (35 -67)
Clinical Trial Not Applicable
RSV-associated hospitalizationNirsevimab*VISION 79 (67 -87)
NVSN 82 (71 -88)
Clinical Trial 81 (62 -90)
Maternal Vaccine†VISION 79 (55 -90)
NVSN 70 (28 -88)
Clinical Trial 57 (15 -80)
RSV-associated Intensive Care
Unit (ICU) admissionNirsevimab*VISION 82 (57 -93)
NVSN 88 (63 -96)
Overcoming 80 (73 -85)
Clinical Trial 90 (16 -99)
*Jones et al. MMWR 2023. Available: https://www.cdc.gov/mmwr/volumes/72/wr/mm7234a4.htm
†Kampmann et al. NEJM 2023. Available: https://www.nejm.org/doi/full/10.1056/NEJMoa2216480 170 20 40 60 80 100
Vaccine Effectivness (%)
•Nirsevimab was effective against RSV -associated
emergency department (ED) encounters,
hospitalization, and critical illness among infants
in their first RSV season during the 2024 –2025
RSV season in the United States.
•Maternal vaccination was effective against RSV -
associated ED encounters and hospitalization
during the 2024 –2025 RSV season in the United
States.
•Ongoing monitoring of post -licensure nirsevimab
and maternal RSV vaccine effectiveness will be
necessary to assess additional outcomes.Product Effectiveness Conclusions
18
Impact of RSV prevention products on U.S.
pediatric RSV -associated hospitalizations
Analyzed data from two active, population -based U.S. surveillance systems
that monitor laboratory -confirmed RSV -associated hospitalizations
RSV-NET NVSN
RESP -NET: Respiratory Virus Hospitalization
Surveillance Network
•RSV-NET, FluSurv -NET, COVID -NET
•Patients of any age from >300 hospitals, 161
counties in 13 states
•https://www.cdc.gov/rsv/php/surveillance/rsv -net.htmlNVSN: New Vaccine Surveillance Network
•Children <18 years old hospitalized with acute
respiratory illness at 7 academic pediatric health
systems in 7 states
•https://www.cdc.gov/nvsn/php/about/index.html
20
Methods
•Ecological analysis that compared RSV -associated hospitalizations and rates between
RSV seasons before and after RSV prevention product introduction
‒Pre-pandemic, before product introduction
▪RSV-NET: 2018 –19, 2019 –20
▪NVSN: 2017 –19, 2018 –19, 2019 –20
‒After product introduction
▪2024 –25, 2nd year of product availability
•Excluded RSV seasons
‒2020 –21, 2021 –22, and 2022 –23 seasons impacted by COVID -19 pandemic
‒2023 –24, 1st year of product availability
▪Low product availability and uptake21
Methods
•Compared adjusted RSV -associated hospitalization and ICU admission rates *
before and after RSV prevention product introduction
–Weekly (RSV -NET) and monthly (NVSN) hospitalization rates during 2024 –25
versus same periods in prior seasons
–Cumulative 2024 –25 hospitalization rates compared to pooled rates from prior
seasons
▪Hospitalization rates (RSV -NET and NVSN)
▪ICU admission rates (RSV -NET)
–Estimated rate ratios (RR) comparing cumulative rates
–Estimated relative rate reductions (RRR): (1 -RR) x 100
*RSV -NET rates adjusted for undertesting and test sensitivity; NVSN rates adjusted for enrollment rates, weeks with <7 surveillance days, test sensitivity, and hospital market share
22
•Assessed changes in rates before and after RSV prevention
product introduction for three age groups with different RSV
prevention optionsMethods
23
•Assessed changes in rates before and after RSV prevention
product introduction for three age groups with different RSV
prevention options
‒Infants aged 0 –7 months
▪Eligible for nirsevimab
▪Potentially protected by maternal RSV vaccinationMethods
24
•Assessed changes in rates before and after RSV prevention
product introduction for three age groups with different RSV
prevention options
‒Infants aged 0 –7 months
▪Eligible for nirsevimab
▪Potentially protected by maternal RSV vaccine
‒Children aged 8 –19 months
▪Small number may have been eligible for
nirsevimab based on risk conditionsMethods
25
•Assessed changes in rates before and after RSV prevention
product introduction for three age groups with different RSV
prevention options
‒Infants aged 0 –7 months
▪Eligible for nirsevimab
▪Potentially protected by maternal RSV vaccine
‒Children aged 8 –19 months
▪Small number may have been eligible for
nirsevimab based on risk conditions
‒Children aged 20 –59 months
▪Age group ineligible for RSV prevention productsMethods
26
•Assessed changes in rates before and after RSV prevention
product introduction for three age groups with different RSV
prevention options
‒Infants aged 0 –7 months
▪Eligible for nirsevimab
▪Potentially protected by maternal RSV vaccine
‒Children aged 8 –19 months
▪Small number may have been eligible for
nirsevimab based on risk conditions
‒Children aged 20 –59 months
▪Age group ineligible for RSV prevention productsMethods
Comparison populations
mostly ineligible for RSV
prevention products.
Included to detect
hospitalization rate
changes unrelated to
RSV product uptake.
27
https://www.cdc.gov/rsvvaxview/dashboard/nirsevimab -coverage -infants.htmlDuring 2024 –25, RSV prevention products were available before RSV season
onset in most states, with product coverage that increased over time.
•21% to 48% coverage among infants aged
0–7 months across 36 reporting
jurisdictions as of March 2025
•39% of eligible* pregnant women aged
18–49 years received RSV vaccine as of
January 2025Nirsevimab Maternal RSV Vaccine
*includes pregnant women who reached at least 32 weeks’ gestation as of September 1, 2024
https://www.cdc.gov/rsvvaxview/dashboard/pregnant -women -coverage.htmlIIS Nirsevimab Coverage (%)
for 2024–25 Season
28
2018–19
Rate2019–20
Rate2024–25
RateInfants
vs vs2018–19
Rate2019–20
Rate2024–25
Ratevs vs2018–19
Rate2019–20
Rate2024–25
Ratevs vsToddlers ChildrenFor an ecological analysis, RSV -associated hospitalization rates can be assessed in three age
groups across different RSV seasons
29
In the absence of new RSV prevention products, RSV -associated hospitalization rates would be
expected to vary by age group, but remain consistent within each age group across seasons.
2018–19
Rate2019–20
Rate2024–25
RateInfants
vs vs2018–19
Rate2019–20
Rate2024–25
Ratevs vs2018–19
Rate2019–20
Rate2024–25
Ratevs vsToddlers Children
30
Because new RSV prevention products are only recommended for some children, RSV -associated hospitalization rates
from seasons before product introduction can be compared to 2024 –25 (after product introduction), by age group
2018–19
Rate2019–20
Rate2024–25
Ratevs vs2018–19
Rate2019–20
Rate2024–25
Ratevs vs2018–19
Rate2019–20
Rate2024–25
Ratevs vsInfants aged 0 –7 months, eligible
for nirsevimab or potentially
protected by maternal RSV vaccineChildren aged 8 –19 months, some of
whom may have been eligible for nirsevimab
based on risk conditionsChildren aged 20 –59 months, age
group ineligible for RSV prevention
products
31
The analysis can assess whether RSV -associated hospitalization rates in 2024 –25 compared to prior
seasons changed more for infants aged 0 –7 months than for children aged 8 –19 and 20 –59 months
2018–19
Rate2019–20
Rate2024–25
Ratevs vs2018–19
Rate2019–20
Rate2024–25
Ratevs vs2018–19
Rate2019–20
Rate2024–25
Ratevs vsInfants aged 0 –7 months, eligible
for nirsevimab or potentially
protected by maternal RSV vaccineChildren aged 8 –19 months, some of
whom may have been eligible for nirsevimab
based on risk conditionsChildren aged 20 –59 months, age
group ineligible for RSV prevention
products
32
Results
Combined, RSV -NET and NVSN identified >20,000 children
aged <5 years with RSV -associated hospitalizations
RSV-NET NVSN
2018–20 2024–25 2017–20 2024–25 Total*
Hospitalizations 9,717 7,003 3,119 1,001 20,840
Intensive Care Unit (ICU)
Admissions2,332 251 671 200 3,454
34*Children at two surveillance sites for NVSN and RSV -NET could be documented in both systems. In 2018 –20, 252 hospitalized child ren were enrolled in both systems, with 54 also having an ICU
admission. During 2024 –25, 76 children were enrolled in both systems with 25 having an ICU admission.
Proportions of children aged <5 years with an RSV -associated
hospitalization who were aged 0–7 months decreased, and median age
increased, in 2024 –25 compared to seasons before product introduction
28
1431
1523
1525
22
0102030405060708090100
2018–20 2024–25 2017–20 2024–25Proportion of all children aged <5 years with RSV -associated
hospitalizationChildren aged 20 –59 months
Children aged 8 –19 months
Infants aged 3 –7 months
Infants aged 0 –2 months
Median age in months 7.7 15.4 6.3 12.7RSV-NET NVSN
29%38%51%46%
35
Cumulative adjusted RSV -associated hospitalization rates in 2024 –25
were compared to seasons before product introduction by age group
17.016.0
5.85.3
1.71.1
02468101214161820
RSV-NET NVSN RSV-NET NVSN RSV-NET NVSN
0–7 months 8–19 months 20–59 monthsHospitalization rate per 1,000 children2018-20
(RSV-NET) or
2017-20
(NVSN)
Patton & Moline et al, MMWR 2025; Curns et al. Pediatrics 202436Bar labels indicate cumulative laboratory -confirmed RSV -associated hospitalizations per 1,000 children as of April 30 (RSV -NET) or March 31 (NVSN) ea ch season. Rates use U.S. population denominators. RSV -NET rates are adjusted to account for RSV underdetection because of
testing practices and test sensitivity. NVSN rates are adjusted to account for weeks with <7 days of surveillance, the proportion of eligible children not enrolled, sensitivity of respiratory syncytial virus reverse -transcription polymerase chain reaction testing compared to serology,
and each site’s estimated market share of acute respiratory illness hospitalizations by age. Error bars denote 95% confidence intervals (95% CI).
Cumulative adjusted RSV -associated hospitalization rates in 2024 –25
were compared to seasons before product introduction by age group
17.016.0
5.85.3
1.71.110.511.0
8.1
6.3
2.9
1.9
02468101214161820
RSV-NET NVSN RSV-NET NVSN RSV-NET NVSN
0–7 months 8–19 months 20–59 monthsHospitalization rate per 1,000 children2018-20
(RSV-NET) or
2017-20
(NVSN)
2024-25
37
Patton & Moline et al, MMWR 2025; Curns et al. Pediatrics 2024Bar labels indicate cumulative laboratory -confirmed RSV -associated hospitalizations per 1,000 children as of April 30 (RSV -NET) or March 31 (NVSN) ea ch season. Rates use U.S. population denominators. RSV -NET rates are adjusted to account for RSV underdetection because of
testing practices and test sensitivity. NVSN rates are adjusted to account for weeks with <7 days of surveillance, the proportion of eligible children not enrolled, sensitivity of respiratory syncytial virus reverse -transcription polymerase chain reaction testing compared to serology,
and each site’s estimated market share of acute respiratory illness hospitalizations by age. Error bars denote 95% confidence intervals (95% CI).
RRR=relative rate reduction, 95%CI = 95% confidence interval
Bar labels indicate cumulative laboratory -confirmed RSV -associated hospitalizations per 1,000 children as of April 30 (RSV -NET) or March 31 (NVSN) each season. Rates use U.S. population denominators. RSV -NET rates are adjusted to account for RSV underdetection because of
testing practices and test sensitivity. NVSN rates are adjusted to account for weeks with <7 days of surveillance, the proportion of eligible children not enrolled, sensitivity of respiratory syncytial virus reverse -transcription polymerase chain reaction testing compared to serology,
and each site’s estimated market share of acute respiratory illness hospitalizations by age. Error bars denote 95% confidence intervals.Among infants aged 0–7 months (eligible for p rotection by nirsevimab or
maternal vaccine ) RSV -associated hospitalization rates were reduced by 38% and
31% in 2024–25 compared to seasons before product introduction
17.016.0
5.85.3
1.71.110.511.0
8.1
6.3
2.9
1.9
02468101214161820
RSV-NET NVSN RSV-NET NVSN RSV-NET NVSN
0–7 months 8–19 months 20–59 monthsHospitalization rate per 1,000 children2018-20
(RSV-NET) or
2017-20
(NVSN)
2024-25RRR=31%
(95% CI 22 -44)RRR=38%
(95% CI 35 -41)
No reductions
38
Patton & Moline et al, MMWR 2025; Curns et al. Pediatrics 2024
Bar labels indicate cumulative laboratory -confirmed RSV -associated hospitalizations per 1,000 children as of April 30 (RSV -NET) or March 31 (NVSN) each season. Rates use U.S. population denominators. RSV -NET rates are adjusted to account for RSV
underdetection because of testing practices and test sensitivity. NVSN rates are adjusted to account for weeks with <7 days of surveillance, the proportion of eligible children not enrolled, sensitivity of respiratory syncytial virus reverse -transcription polymerase
chain reaction testing compared to serology, and each site’s estimated market share of acute respiratory illness hospitalizat ions by age. Error bars denote 95% confidence intervals.Cumulative adjusted RSV -associated hospitalization rates in 2024 –25
were compared to prior seasons among subgroups of infants aged 0 –2
and 3–7 months
24.923.4
12.211.5
051015202530
RSV-NET NVSN RSV-NET NVSN
0–2 months 3–7 monthsHospitalization rate per 1,000 children2018-20
(RSV-NET) or
2017-20
(NVSN)
Patton & Moline et al, MMWR 2025; Curns et al. Pediatrics 202439
RRR=relative rate reduction, 95%CI = 95% confidence interval
Bar labels indicate cumulative laboratory -confirmed RSV -associated hospitalizations per 1,000 children as of April 30 (RSV -NET) or March 31 (NVSN) each season. Rates use U.S. population denominators. RSV -NET rates are adjusted to account for RSV
underdetection because of testing practices and test sensitivity. NVSN rates are adjusted to account for weeks with <7 days of surveillance, the proportion of eligible children not enrolled, sensitivity of respiratory syncytial virus reverse -transcription polymerase
chain reaction testing compared to serology, and each site’s estimated market share of acute respiratory illness hospitalizat ions by age. Error bars denote 95% confidence intervals.RSV-associated hospitalization rates were reduced by 47% in RSV -NET
and 46% in NVSN among infants aged 0 –2 months in 2024 –25
compared to seasons before product introduction
24.923.4
12.211.513.212.6
8.910.1
051015202530
RSV-NET NVSN RSV-NET NVSN
0–2 months 3–7 monthsHospitalization rate per 1,000 children2018-20
(RSV-NET) or
2017-20
(NVSN)
2024-25RRR= 47% (95% CI 43 -50) RRR= 46% (95% CI 35 -57)
RRR= 27% (95% CI 22 -32)RRR=20% (95% CI -4-37)
Patton & Moline et al, MMWR 2025; Curns et al. Pediatrics 202440
Conclusions
RSV Prevention Product Impact Conclusions
•Two U.S. population -based surveillance
networks demonstrated reductions in RSV -
associated hospitalization rates during 2024 –25
among infants eligible for RSV prevention
product protection
-38% (RSV -NET) and 31% (NVSN) reductions in
2024 –25 compared to RSV seasons before product
introduction among infants aged 0 –7 months
42
Conclusions
•Reductions in RSV -associated hospitalization were
greatest among infants aged 0 –2 months born just
before or during the RSV season
-47% (RSV -NET) and 46% (NVSN) reductions in 2024 –25
-Group at highest risk of hospitalization
-Underscores importance of protection through maternal
vaccination during pregnancy or nirsevimab in first week
of life
•Ongoing monitoring of RSV disease trends —including
severity and age distribution —is critical to assess
sustained impact of RSV prevention products
43
Acknowledgements
▪CDC National Center for Immunizations and Respiratory
Diseases (NCIRD)
▪CDC -funded partners
•VISION
•New Vaccine Surveillance Network (NVSN)
•Overcoming Network
•RSV-NET
44
www.cdc.govFor more information, contact CDC
1-800 -CDC -INFO (232 -4636)
TTY: 1 -888 -232-6348 www.cdc.gov
The findings and conclusions in this report are those of the authors and do not necessarily represent the official
position of the Centers for Disease Control and Prevention.
Photographs and images included in this presentation are licensed solely for CDC/NCIRD online and presentation
use. No rights are implied or extended for use in printing or any use by other CDC CIOs or any external audiences.
Bar labels indicate the incidence rate per 1,000 children. Rates were calculated using county -specific denominators from the 20 20 US bridged -race population estimates, and population -based numerators based on the observed number of hospitalizations at eac h site adjusted to
account for weeks with <7 days of surveillance, the proportion of eligible children not enrolled, sensitivity of respiratory syncytial virus reverse -transcription polymerase chain reaction testing compared to serology, and each site’s estimated market shar e of ARI hospitalizations by age.
Error bars denote 95% confidence intervals determined based on 1000 bootstrap samples for each rate.RSV-associated hospitalization rates among children <5 years of
age, by season, New Vaccine Surveillance Network, 2017 -2025
Curns et al. Pediatrics 2024; Patton & Moline et al, MMWR 2025.
25.67
13.35
8.41
4.07
1.104.1919.1
12.0
5.3
2.9
0.73.027.0
15.7
8.0
4.4
1.24.423.9
13.7
7.2
3.8
1.03.926.6
16.2
8.7
5.2
1.65.012.0
10.7
6.3
5.8
1.43.7
05101520253035
0-2 Months 3-5 months 6-11 months 12-23 months 24-59 months 0-59 monthsHospitalization rate per 1,000 children
Age Group2017-2018
2018-2019
2019-2020
2017-2020 Average
2023-2024
2024-2025
46
Bar labels indicate the incidence rate per 1,000 children. Rates were calculated using county -specific denominators from the 20 20 US bridged -race population estimates, and population -based numerators based on the observed number of hospitalizations at eac h site adjusted to
account for weeks with <7 days of surveillance, the proportion of eligible children not enrolled, sensitivity of respiratory syncytial virus reverse -transcription polymerase chain reaction testing compared to serology, and each site’s estimated market shar e of ARI hospitalizations by age.
Error bars denote 95% confidence intervals determined based on 1000 bootstrap samples for each rate.RSV-associated hospitalization rates among children <5 years of
age, by season, RSV -NET, 2018 –2025
RSV-NET unpublished data
22.1
14.8
8.9
6.5
5.0
1.726.8
15.6
10.3
7.9
5.2
1.9
0.41 0.32 0.14 0.16 0.09 0.0427.0
13.7
9.1
6.6
5.2
1.935.7
24.6
18.4
12.3
10.0
4.222.9
16.8
13.6
10.4
7.3
2.613.2
9.8
8.5 8.77.8
2.9
0510152025303540
0-2 months 3-5 months 6-7 months 8-11 months 12-19 months 20-59 monthsHospitalization rate per 1,000 children2018-19 2019-20 2020-21 2021-22 2022-23 2023-24 2024-25
47
RSV-NET NVSNWeekly (RSV -NET) and monthly* (NVSN) adjusted RSV -associated hospitalization rates in 2024 –25 were lower compared to
prior seasons among infants aged 0–7 months and
were the same or higher than prior seasons among children aged 20–59 months
00.20.40.60.811.21.41.61.8
40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18Adjusted RSV hospitalization rate per 1,000 population
Surveillance week2024-25 Pooled 2018 –2020
Minimum 2018 –2020 Maximum 2018 –2020
00.20.40.60.811.21.41.61.8
40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18Adjusted RSV hospitalization rate per 1,000 population
Surveillance week2024-25 Pooled 2018 –2020
Minimum 2018 –2020 Maximum 2018 –2020
00.20.40.60.811.21.41.61.8
40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18Adjusted RSV hospitalization rate per 1,000 population
Surveillance week2024-25 Pooled 2018 –2020
Minimum 2018 –2020 Maximum 2018 –2020Infants aged 0 –7 months
Eligible for protection by nirsevimab or
maternal vaccineChildren aged 8 –19 months
Small number eligible for nirsevimabChildren aged 20 –59 months
Ineligible for either product
0123456
October† November December January February March† April†Monthly RSV -associated hospitalization rate per 1,000 population
Month of RSV Season2024 –25 Pooled 2017 –2020
Minimum 2017 –2020 Maximum 2017 –2020
0123456
October November December January February March† AprilMonthly RSV -associated hospitalization rate per 1,000 population
Month of RSV Season2024 –25 Pooled 2017 –2020
Minimum 2017 –2020 Maximum 2017 –2020
0123456
October November December January February March† April†Monthly RSV -associated hospitalization rate per 1,000 population
Month of RSV Season2024 –25 Pooled 2017 –2020
Minimum 2017 –2020 Maximum 2017 –2020
48
Patton & Moline et al, MMWR 2025*2024 -25 NVSN rates through March 31, 2025. †NVSN rates should be interpreted with caution as relative standard error ≥30 or n <5: 0 –7 months March 2024 -25, 8 –19 months Mar ch 2017 –20 max, 20 –59 months October, March and April 2017 –20 min and April 2017 –20 pooled
RSV-NET rates are adjusted to account for RSV underdetection because of testing practices and test sensitivity. NVSN rates are adjusted to account for weeks with <7 days of surveillance, the proportion of eligible children not enrolled, sensitivity of respiratory syncytial virus reverse -transcription polymerase chain reaction
testing compared to serology, and each site’s estimated market share of acute respiratory illness hospitalizations by age.
RRR=relative rate reduction, 95%CI = 95% confidence interval
Bar labels indicate cumulative laboratory -confirmed RSV -associated hospitalizations per 1,000 children as of April 30 (RSV -NET) or March 31 (NVSN) each season. Rates use U.S. population denominators. RSV -NET rates are adjusted to account for RSV
underdetection because of testing practices and test sensitivity. NVSN rates are adjusted to account for weeks with <7 days of surveillance, the proportion of eligible children not enrolled, sensitivity of respiratory syncytial virus reverse -transcription polymerase
chain reaction testing compared to serology, and each site’s estimated market share of acute respiratory illness hospitalizat ions by age. Error bars denote 95% confidence intervals.RSV-associated ICU admission rates in RSV -NET were reduced by 38%
among infants aged 0–7 months ; no reductions occurred among
children aged 8 –19 and 20 –59 months
5.2
1.4
0.43.2
1.3
0.4
0123456
0–7 months 8–19 months 20–59 monthsICU admission rate per 1,000 children2018-20
2024-25RRR= 38% (95% CI 32 -43)
No reductions
RSV-NET unpublished data49
8.2
3.44.8
2.3
012345678910
0–2 months 3–7 monthsICU admission rate per 1,000 children2018-20
2024-25RRR= 42% (95% CI 34 -48)RSV-associated ICU admission rates in RSV -NET were reduced by 42%
among infants aged 0 –2 months and by 31% among infants aged 3 –7
months
RRR=31% (95% CI 21 -40)
50
RSV-NET unpublished dataRRR=relative rate reduction, 95%CI = 95% confidence interval
Bar labels indicate cumulative laboratory -confirmed RSV -associated hospitalizations per 1,000 children as of April 30 (RSV -NET) or March 31 (NVSN) ea ch season. Rates use U.S. population denominators. RSV -NET rates are adjusted to account for RSV
underdetection because of testing practices and test sensitivity. NVSN rates are adjusted to account for weeks with <7 days of surveillance, the proportion of eligible children not enrolled, sensitivity of respiratory syncytial virus reverse -transcription polymerase
chain reaction testing compared to serology, and each site’s estimated market share of acute respiratory illness hospitalizat ions by age. Error bars denote 95% confidence intervals.
Meta -analysis of nirsevimab effectiveness against
RSV-associated hospitalization, 2023 -2024 season
PE (95% CI)
79 (72 -85)
77 (65 -86)
76 (65 -83)
85 (72 -92)
66 (62 -70)
99 (76 -100)
71 (39 -86)
90 (86 -93)
81 (63 -90)
85 (23 -97)
90 (84 -93)
71 (58 -81)
80 (76 -83)
93 (84 -97)
95 (89 -98)
86 (66 -95)
83 (77 -88)
Sumsuzzman DM et al. Real -world effectiveness of nirsevimab against respiratory syncytial virus disease in infants: a systematic review and meta -analysis. Lancet Child Adolesc Health 2025
PE: Product Effectiveness; CI: Confidence IntervalVISION 79 (67 -87)
NVSN 82 (71 -88)
51
Meta -analysis of nirsevimab effectiveness against
RSV-associated ICU admission, 2023 -2024 season
Sumsuzzman DM et al. Real -world effectiveness of nirsevimab against respiratory syncytial virus disease in infants: a systematic review and meta -analysis. Lancet Child Adolesc Health 2025
PE: Product Effectiveness; CI: Confidence Interval
PE (95% CI)
84 (49 -95)
52 (-17-87)
75 (51 -87)
66 (42 -80)
74 (56 -85)
93 (84 -97)
86 (72 -93)
84 (69 -92)
92 (78 -97)
81 (71 -88)
VISION 82 (57 -93)
NVSN 88 (63 -96)
OC 79 (62 -89)
52
•Argentina
-Razzini et al.1: VE against RSV-associated hospitalization was 81% (95% CI 63 –91) among infants
under age 3 months
-Perez Marc et al.2: VE against RSV-associated hospitalization was 79% (95% CI 62 –88) among
infants under age 3 months
-Gentile et al.3: VE against RSV-associated hospitalization was 79% (95% CI: 51 –91) among infants
under age 6 months
•UK
-Williams et al.4: VE against RSV-associated hospitalization was 72% (95% CI: 48 –85) among infants
under age 3 monthsMaternal RSV vaccine effectiveness estimates from
Argentina and UK
1Razzini JL et al. Impact and Effectiveness of Universal Respiratory Syncytial Virus Vaccination During Pregnancy on Infant Ho spitalizations in Buenos Aires: A Retrospective Cohort Study. VeriXiv . 2025
2Pérez Marc G et al. Real -world effectiveness of RSVpreF vaccination during pregnancy against RSV -associated lower respiratory tract disease leading to hospitalisation in infants during the 2024 RSV season in
Argentina (BERNI study): a multicentre , retrospective, test -negative, case –control study. The Lancet Infectious Diseases. 2025
3Gentile A et al. Maternal Immunization With RSVpreF Vaccine: Effectiveness in Preventing Respiratory Syncytial Virus –associated Hospitalizations in Infants Under 6 Months in Argen tina: Multicenter Case –control
Study. The Pediatric Infectious Disease Journal . 2025
4Williams TC et al. Bivalent Prefusion F Vaccination in Pregnancy and Respiratory Syncytial Virus Hospitalisation in Infants: Results of a Prospective, Multi -Centre, Test -Negative Study. Available at SSRN:
https://ssrn.com/abstract=5184994 or http://dx.doi.org/10.2139/ssrn.5184994 53
•Models did not adjust for healthcare utilization behavior or specific
underlying characteristics between vaccinated and unvaccinated patientsProduct Effectiveness Analyses – Controlling for
Confounding
54VISION NVSN Overcoming
Analysis Multivariable logistic regression
models, adjusting for site, age in
months, calendar date, race and
ethnicity, and sex.
Models adjusting for underlying
medical conditions did not
meaningfully change estimates.Multivariable logistic regression
models, adjusting for site, age in
months, and month of enrollment.
Nirsevimab analysis adjusted for
presence of ≥1 high -risk medical
condition for severe RSV
disease; maternal RSV analysis
adjusted for race/ethnicity and
insurance status.Multivariable logistic
regression models, adjusting
for site, age in months,
timing of enrollment,
presence of ≥1 underlying
medical condition, and social
vulnerability index.