Economics of Preventing Respiratory Syncytial 

Virus Lower Respiratory Tract Infections (RSVLRTI) among US Infants with Nirsevimab 

A SUMMARY REPORT COMPARING MODELS FROM:

Sanofi AND University of Michigan and CDC

Ismael R. Ortega-Sanchez, PhD

NCIRD/CDC

ACIP Meeting, February 23, 2023 

46

Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of 

the Centers for Disease Control and Prevention. 

National Center for Immunization & Respiratory Diseases
Conflict of interest

• Sanofi model: Alexia Kieffer et al., [complete authors list and 

affiliations, upon request ]

• Sanofi manufactures nirsevimab

• Evidera (San Francisco, London) was funded by Sanofi

• UM-CDC model: David W Hutton et al. from Univ Michigan, ..., 

Ismael R Ortega-Sanchez et al. from CDC [complete authors list and 

affiliations, upon request ]

• All authors: No conflicts of interest

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Overview

Policy questions:

• Should one dose of nirsevimab be recommended 

• a) at birth for all infants born during October to March and

• b) for all infants born during April through September and <8 

months of age when entering first RSV season?

• Should nirsevimab be recommended for children <20 months of age 

entering their second RSV season who remain at increased risk of 

severe disease?

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Economic analysis

Question: Is the use of nirsevimab against RSV LRTI in all infants <8 months entering their first RSV season or born during season (and in high-risk children 

<20 months entering the 2nd season) cost-effective?

Comparator Intervention

Base-case scenario: What is the incremental cost-effectiveness of using nirsevimab in all infants <8 months entering their first RSV season or born during season (and in high-risk 

children <20 months entering second season) relative to “Standard of Care”?

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Standard of care (SoC)

Infants in first season

(and high-risk in 2nd

season)

Giving nirsevimab to

infants in first season

(and high-risk in 2nd

season)

Standard of Care (SoC) = Palivizumab only for infants eligible as per AAP recommendations, and no immunization for all other pre-term 

and term infants
Focus on key features for model comparison

• Modeling approach

• Targeted population(s)

• Perspective (healthcare vs. societal)

• Intervention strategies and comparators

• Inputs for RSV disease burden, nirsevimab efficacy, and costs

• Incidence of RSV disease, rates of outcomes 

• Direct and indirect costs of RSV disease

• Intervention: efficacy, duration of protection, safety and program costs

• Assumptions

• Strong, influential assumptions

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51

Modeling design and assumptions

Sanofi UM-CDC

Static analytical decision-making models ✔ ✔

Sensitivity analyses (and probabilistic simulation) ✔(✔) ✔

Hypothetical population: All infants < 8 months (high risk children 8-19 

months)

✔(✔) ✔(✔)

Time Frame: First year after a dose of nirsevimab

(2nd season, 2nd dose for high-risk 8-19 months only)

✔

(✔)

✔

(✔)

Analytic Horizon: two years or seasons (for temporary disability) and 

Life Expectancy (for premature mortality)

✔

✔

✔

✔

Discount rate: 3% ✔ ✔

Year of economic outcomes measured: 2022 ✔ ✔

Societal perspective (and healthcare perspective) ✔(✔) ✔(✔)
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Inputs and main outcomes

Prevention of:

• MA RSV LRTI

• RSV LRTI hospitalizations

• RSV-associated deaths

QALYs saved

$/QALY saved

Number needed to

immunize (NNI) to avert an:

• MA RSV LRTI

• RSV LRTI hospitalization

• RSV-associated death

Sanofi UM-CDC

✔ ✔

✔ ✔

✔ ✔

✔ ✔

✔ ✔

✔ ✔

✔ ✔

✔ ✔

HCRU = health care resource use, MA = Medically attended, LRTI= Lower respiratory tract infection, QALY= quality-adjusted life year
Sanofi model: Base case estimates for all infants <7 

months in Season 1, nirsevimab cost $500/dose & PSA

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Summary outcomes Base-Case

$/QALY gained $70,430

$/RSV MA LRTI case averted $798

$/RSV-associated LRTI 

hospitalization averted $9,387

$/RSV-assoc. death averted >$5.6Million

NNI to avert an RSV-MA LRTI 

case 5

NNI to avert an RSVassociated LRTI hospitalization 43

NNI to avert a death 55,957

Probabilistic sensitivity analysis (PSA)

Base case
UM-CDC: Base case estimates for all infants <8 

months, Season 1, nirsevimab cost $300/dose 

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Cost per type of health outcome prevented 

Summary outcomes Base-Case

$/QALY gained $102,805

$/RSV-MA LRTI case averted $2,100

$/RSV-associated 

LRTI hospitalization averted $18,881

$/RSV-assoc. death averted n/r

NNI avert an RSV-MA LRTI 

case 14

NNI avert an RSV-assoc. LRTI 

hospitalization 130

NNI avert an RSV-assoc. death n/r

Assuming 100% uptake in nirsevimab group

n/r = not reported

$2,528 

$7,096 

$18,881 

$85,822 

$3,496 

$28,607 

 $-

 $10,000

 $20,000

 $30,000

 $40,000

 $50,000

 $60,000

 $70,000

 $80,000

 $90,000

 $100,000

Outpatient ED Inpatient ICU Inpatient

Day

ICU Day

Cost per Event Averted
Sanofi and UM-CDC models comparison: 

Selected outcome ratios for nirsevimab

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UM-CDC model

Price per dose $300

Sanofi model

Price per dose $500

$ / QALY gained

nirsevimab Season 1, infants $102,805 $70,430

nirsevimab Season 2, high risk infants $842,139b $823,131a

nirsevimab Seasons 1 & 2 combined n/r $62,589

nirsevimab vs palivizumab, Season 2 PEPc n/r dominant

$ / hospitalization averted

nirsevimab Season 1 $18,881 $9,387

nirsevimab Seasons 1 & 2 combined n/r $8,316

a. Pre-term infants only

b. High risk <19 months old infants (preterm + PEP) receiving a 2nd dose of nirsevimab in October

c. PEP= palivizumab eligible population 

n/r = not reported
UM-CDC model: One-way Sensitivity Analyses (Season 1 only)

Base case: $102,805/QALY saved, nirsevimab cost $300/dose

56 Assuming 100% uptake in nirsevimab group

$0 $50,000 $100,000 $150,000 $200,000 $250,000 $300,000 $350,000

Nirsevimab cost/dose

RSV QALYs lost Hospitalized RSV QALYS Lost

Initial Efficacy

RSV QALYs lost Outpatient Child

Proportion of RSV infections with an LRTI diagnosis Outpatient Age 0-5 months

RSV QALYs lost Outpatient Child caregiver

Proportion of RSV infections with an LRTI diagnosis Hospitalizations Age 0-5 months

Proportion of RSV infections with an LRTI diagnosis ED Visits Age 0-5 months

RSV QALYs lost ED Child

Proportion of RSV infections with an LRTI diagnosis Outpatient Age 6-11 months

Low High

Nirsevimab cost/dose

RSV QALYs lost by a child while hospitalized

Initial vaccine efficacy

RSV QALYs lost by an outpatient’s caregiver

Proportion of RSV infections with an LRTI diagnosis in outpatient visits (age 0-5 months)

RSV QALYs lost by a child as an outpatient 

Proportion of RSV infections with an LRTI diagnosis in hospitalizations (age 0-5 months) 

Proportion of RSV diagnosis in an LRTI diagnosis in ED visits (age 0-5 months)

RSV QALYs lost by a child as ED patient 

Proportion of RSV LRTI diagnosis in outpatients visits (age 6-11 months)
Sanofi model: One-way Sensitivity Analyses (Season 1 only)

Base case: $70,430/QALY saved, nirsevimab cost $500/dose

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Sanofi and UM-CDC models comparison: 

Selected influential inputs 

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• RSV-hospitalization rate

Sanofi: Age and term-specific hospitalization rates reported in McLaurin (2016)a

UM-CDC: From RSV-associated hospitalization ratesb among children aged ≤2 years

• Unitary medical cost of RSV hospitalization

Sanofi: Cost varies by term at birth and by whether Intensive Care Unit or Mechanical Ventilator were needed 

as reported in McLaurin (2016)b

UM-CDC: Unit cost was a weighted average by term at birth and age as reported in Bowser (2022)c

• RSV season & intervention period

Sanofi: MA RSV season based on Rainisch (2020)d but intervention ends in February

UM-CDC: RSV-season and intervention period based on CDC surveillance data (2016-2019)c

• Initial efficacy & waning

Sanofi: Constant first 5 months as in trials, linear decay from month 6 to month 10

UM-CDC: Sigmoid decay up to 10 months; average residual protection in first 5 months equals constant 

efficacy from trials

a McLaurin et al. J Perinatol. 2016;36(11):990-996

b CDC unpublished data from the New Vaccine Surveillance Network (NVSN) (December 2016 to September 2020)

c Bowser et al., J Infect Dis. 2022 Aug 15; 226(Suppl 2): S225–S235

d Rainisch et al. Vaccine. 2020;38(2):251-257
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UM-CDC Sanofi

Risk of RSV hospitalization (Infants <12 

months of age)

1.30% 

(0.60% - 3.11%)a

1.42% 

(0.49% - 4.37%)b

Medical costs per RSV hospitalization $11,487

($11,042 - $11,993)c

$18,790 – $28,812

(age- and term dependent)d

Medical costs per RSV outpatient visit $82 

($46 - $118)c

$153 

(no variation reported)

a Data from CDC-funded New Vaccine Surveillance Network (NVSN) (December 2016 to September 2020) (range values are the lowest and highest within the first 11 months of age)

b Weighted average term-specific populations shares (range values are the lowest and highest within the first 11 months of age)

c Adapted from Bowser et al., J Infect Dis. 2022 Aug 15; 226(Suppl 2): S225–S235 (A systematic review study funded by Sanofi)

d Costs in the base-case varied by age, term at birth and by whether Intensive Care Unit or Mechanical Ventilator were needed while hospitalized using percentages as wights; data reported 

in McLaurin (2016)

Sanofi and UM-CDC models comparison: 

Differences in key inputs
Sanofi and UM-CDC models comparison: 

Base-case risk of RSV-related hospitalization by age

60

0.00%

0.50%

1.00%

1.50%

2.00%

2.50%

3.00%

3.50%

4.00%

4.50%

5.00%

0 months 1 months 2 months 3 months 4 months 5 months 6 months 7 months 8 months 9 months 10 months 11 months

Risk of Hospitalization 

Age in months

UM-CDC Sanofi

UM-CDC model: Laboratoryconfirmed RSV-associated 

hospitalization rates from New 

Vaccine Surveillance Network 

(NVSN) data for children under 2 

years of age (December 2016 to 

September 2020)

Sanofi model: Age and termspecific weighted average of 

hospitalization rates in infants 

using reported rates in McLaurin 

(2016)
0%

5%

10%

15%

20%

25%

30%

35%

Percent of annual cases

Month of season

UM-CDC

Sanofi

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Sanofi intervention

UM-CDC intervention

Sanofi and UM-CDC models comparison: 

RSV-season and intervention* 

Sanofi

Intervention

UM-CDC 

Intervention

WiS (Within RSV 

season). All Infants 

born in-season

(i.e., October 1st to 

Feb 29th)

At birth, if born 

October 1st

to 

March 31st

WiS: All infants 0-3 

months of age at the 

start of RSV season 

(i.e., in October)

In October, if born in 

April

June

August

OoS (Out of RSV 

season): All infants 

born OoS at the start 

of the RSV season 

(i.e., in October) 

In November, if born 

in 

May

July

September

* RSV-season and Intervention period in UM-CDC model are based on NREVVS seasonality (2016-2019). 

Intervention period in Sanofi model ends in February ( a month short from end of MA RSV season, Rainisch et al., Vaccine. 2020;38(2):251-257. Technical appendix)
Sanofi and UM-CDC: Initial nirsevimab efficacy 

and uptake 

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a MELODY trial and Phase 2b recommended dose

b Assumed non-inferiority with palivizumab, Hammitt et al., N Engl J Med. 2022;386(9):837-846

UM-CDC Sanofi

Initial efficacy against MA RSV LRTI: 

Inpatient and outpatient (%)a

80.0

(68.5 – 86.1)a

79.0 

(68.5 – 86.1)a, b
0%

20%

40%

60%

80%

100%

0 2 4 6 8 10 12

Efficacy

Months after immunization

Sanofi and UM-CDC: Assumption on duration 

of nirsevimab

63

SanofiInitial efficacy against MA LRTI = A constant 

protection over 5 months, 

Then, a linear decay of efficacy from month 6 

to month 10

No residual protection after 10 months

UM

-CDCInitial efficacy against LRTI = Average 5 months 

efficacy equals to trial estimates

Sigmoid decay up to 10 months 

and then 0% afterwards; 

Calibrated such that the first 5 months efficacy 

equals trial estimates
UM-CDC model: comparison of base case & 

selected scenarios

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a Base-case nirsevimab cost $300 per dose, immunization is for only the 1st season 

b LRTI=Lower respiratory tract infection, URTI= Upper respiratory tract infection

c Cost per QALY saved estimated by varying nirsevimab cost per dose from $200 (low) to $500 (high), immunization is for only the 

1st season 

Scenario UM-CDC

Nirsevimab cost per $500/dose (1st season)c $244,677

Intervention period October to February $107,963

Base case a (Nirsevimab cost $300/dose, 1st season) $102,805

Prevention of All MA RSV visits (LRTI and URTI)b $45,092

Nirsevimab cost per $200/dose (1st season)c $31,869
Limitations

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• Factors not considered that may result in overestimating the ICER 

(underestimating the cost-effectiveness) of nirsevimab immunization

• In base-case: both models assumed 

• No protection against URTI 

• No protection against asymptomatic/unattended LRTI 

• Neither model included RSV-related costs incurred after discharge from an 

RSV-associated hospitalization or emergency department visit: 

• Productivity losses incurred by caregivers after discharge

• Both models assumed no indirect effects of nirsevimab immunization (i.e., no 

protection against RSV transmission)
Conclusion

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• Differences in key inputs among Sanofi and UM-CDC models explain differences in results:

• Nirsevimab cost per dose

• Seasonality and intervention period

• Duration of nirservimab efficacy

• Hospitalization rates

• Medical costs

• Base-case in both models:

• Nirsevimab would significantly reduce RSV disease burden in infants

• Data from clinical trials support impact estimates on disease reduction

• Economic value of using nirsevimab in infants could be cost-effective or costly

• Reasonable nirsevimab price and duration of protection combined with careful design of 

seasonal interventions would determine the cost-effectiveness value of routine 

prophylaxis among infants ≤7 months of age entering their first RSV season, and those 

born during the RSV season
Acknowledgements 

From NCIRD/CDC

• Jamison Pike

• Jefferson Jones

• Meredith McMorrow

• Mila M. Prill

• Katherine E. Fleming-Dutra

• Michael Melgar

Also:

• Maternal/Pediatric RSV working group members

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End of Summary