Medical

Safety and Efficacy of 

Bivalent RSV Prefusion F Vaccine 

in Vaccinated Mothers and their Infants

Iona Munjal, MD

Senior Director, Vaccine Research and Development 
178

Worldwide Research, Development and Medical

Vaccine Research and Development

Bivalent RSV Prefusion F Vaccine 

Proposed Indication:

Prevention of lower respiratory 

tract disease and severe lower 

respiratory tract disease caused by 

respiratory syncytial virus (RSV)

DOSE LEVEL

• 120 μg without an adjuvant

• Dose contains 60 μg dose of 

each prefusion protein 

antigen, in a 0.5 mL injection

PRESENTATION

• Single dose 2 mL vial

• 1 mL Pre-filled syringe

• Vial adaptor

STORAGE • Refrigeration at 2°C to 8°C

Infants from birth 

through 6 months of age 

by active immunization 

of pregnant individuals
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Groundbreaking Structural Work by NIH Elucidated that RSV F on the 

Virus Exists as an Unstable Prefusion Form 

Only prefusion F can bind host 

cells for RSV to infect

Antibodies specific to the 

prefusion form are most effective 

at blocking virus infection

McLellan et al. Science, Nov 2013 

Postfusion F Trimer

fused membrane

Prefusion F Trimer

Antigenic Site Ø 

(Nirsevimab, AM22) 

Viral membrane

Antigenic Site II

(Synagis)

Antigenic Site IV 

(101-F, AM14)
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Vaccine Research and Development

2018 2019 2020 2021 2022+

Phase 1/2

First-in-Human1

Adults 18-85y

Dose Ranging

+/- Al(OH)3 +/- Influenza

Phase 2b2

Pregnant Women 18–49y

Safety and Immunogenicity

Early Efficacy

Phase 2b3 Nonpregnant Women 18–49y

Concomitant Tdap

Phase 34 Adults 18-49y

Lot Consistency Study

Phase 35 Pregnant Women ≤49y

Pivotal Efficacy

1. A Study to Describe the Safety and Immunogenicity of a RSV Vaccine in Healthy Adults. NCT03529773.

2. A Phase 2b Placebo-Controlled, Randomized Study of an RSV Vaccine in Pregnant Women. NCT04032093.

3. A Study of an RSV Vaccine When Given Together with Tdap in Healthy Nonpregnant Women Aged Between 18 to 49 Years. NCT04071158.

4. Clinical Lot Consistency for RSVpreF in a Population of Healthy Adults 18 to ≤49 Years of Age. NCT05096208.

5. A Trial to Evaluate the Efficacy and Safety of RSVpreF in Infants Born to Women Vaccinated During Pregnancy. NCT04424316.

Pfizer’s RSVpreF Maternal Immunization Clinical Development Program
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Vaccine Research and Development

2018 2019 2020 2021 2022+

Phase 1/2

First-in-Human1

Adults 18-85y

Dose Ranging

+/- Al(OH)3 +/- Influenza

Phase 2b2

Pregnant Women 18–49y

Safety and Immunogenicity

Early Efficacy

Phase 2b3 Nonpregnant Women 18-49y

Concomitant Tdap

Phase 34 Adults 18-49y 

Lot Consistency Study

Phase 35 Pregnant Women ≤49y

Pivotal Efficacy

1. A Study to Describe the Safety and Immunogenicity of a RSV Vaccine in Healthy Adults. NCT03529773.

2. A Phase 2b Placebo-Controlled, Randomized Study of an RSV Vaccine in Pregnant Women. NCT04032093.

3. A Study of an RSV Vaccine When Given Together with Tdap in Healthy Nonpregnant Women Aged Between 18 to 49 Years. NCT04071158.

4. Clinical Lot Consistency for RSVpreF in a Population of Healthy Adults 18 to ≤49 Years of Age. NCT05096208.

5. A Trial to Evaluate the Efficacy and Safety of RSVpreF in Infants Born to Women Vaccinated During Pregnancy. NCT04424316.

Pfizer’s RSVpreF Maternal Immunization Clinical Development Program
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RSVpreF Elicits Maternal Neutralizing Titer with GMR >12 at Delivery*

Phase 2b Combined A/B 50% Neutralization Geometric Mean Titers & Geometric Mean Ratio vs. Placebo – in Maternal Participants at 

Baseline (24-36 weeks GA), 1M (if Delivery had not Occurred), Delivery and Postpartum; All Evaluable (N=116 participants)

10

100

1000

10000

100000

Baseline 1 Month Delivery 6 Months Postpartum

50% Neutralizing GMT

Placebo 120 μg

17.8

12.4 5.4

Lower Limit of Quantification (LLOQ), RSV A LLOQ, RSV B *Mean time from vaccination to delivery, 61.4 days
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Transplacental Transfer Ratios >1 Overall and by Geography and 

Gestational Age

Combined RSV A/B 50% Neutralization Antibody Infant v. Maternal Ratio for Phase 3 selected dose

Evaluable Population, RSVpreF Groups (N=99)

0.1

1

10

RSV A/B, All

(n=99)

Northern

Hemisphere

(n=88)

Southern

Hemisphere

(n=11)

GA 24 to <27

(n=21)

GA 27 to <30

(n=26)

GA 30 to <33

(n=26)

GA 33 to 36

(n=26)

Neutralizing Titer Transfer Ratio

Geography Maternal Gestational Age at Vaccination
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RSV A/B Combined 50% Geometric Mean Neutralizing Titers by Month in Infants born to Mothers Vaccinated at 24-36 weeks

Infant Neutralizing Titers Remain High Through 6 Months

100

1000

10000

100000

0 1 2 3 4 5 6 7

RSV A/B Combined Serum Neutralizing 

Titer

Months

RSVpreF 120 μg

Placebo

Palivizumab reference

---Palivizumab reference line = 50% A/B neutralizing titer of a 100ug/mL palivizumab dose, demonstrated to be efficacious in preventing infant RSVassociated ICU admission (Forbes ML, Kumar VR, Yogev R, et al. Hum Vaccin Immunother 2014;10:2789-94.)
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Vaccine Research and Development

2018 2019 2020 2021 2022+

Phase 1/2

First-in-Human1

Adults 18-85y

Dose Ranging

+/- Al(OH)3 +/- Influenza

Phase 2b2

Pregnant Women 18–49y

Safety and Immunogenicity

Early Efficacy

Phase 2b3 Nonpregnant Women 18-49y

Concomitant Tdap

Phase 34 Adults 18-49y 

Lot Consistency Study

Phase 35 Pregnant Women ≤49y

Pivotal Efficacy

1. A Study to Describe the Safety and Immunogenicity of a RSV Vaccine in Healthy Adults. NCT03529773.

2. A Phase 2b Placebo-Controlled, Randomized Study of an RSV Vaccine in Pregnant Women. NCT04032093.

3. A Study of an RSV Vaccine When Given Together with Tdap in Healthy Nonpregnant Women Aged Between 18 to 49 Years. NCT04071158.

4. Clinical Lot Consistency for RSVpreF in a Population of Healthy Adults 18 to ≤49 Years of Age. NCT05096208.

5. A Trial to Evaluate the Efficacy and Safety of RSVpreF in Infants Born to Women Vaccinated During Pregnancy. NCT04424316.

Pfizer’s RSVpreF Maternal Immunization Clinical Development Program
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Vaccine Research and Development

A Trial to Evaluate the Efficacy and Safety of RSVpreF in Infants Born to Women Vaccinated During Pregnancy. NCT04424316.

MATISSE: A Phase 3 Trial to Evaluate the Efficacy and Safety of RSVpreF in 

Infants Born to Women Vaccinated During Pregnancy

7,392 Maternal Participants in 18 Countries

Randomized 1:1 RSVpreF 120μg or Placebo

Pregnant persons ≤49 years between 

≥24 and ≤36 weeks gestation

7,128 Infants enrolled
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AEs from Consent to 28 Days

a. Screening bloods and fetal anomaly ultrasound (if not standard of care); ROW, Rest of World

b. Fetal dating and dating ultrasounds (if not standard of care).

c. AESI (AE of Special Interest including preterm delivery and asymptomatic SARS-CoV-2 test positive).

Maternal Immunogenicity & Safety Assessment Timeline

AESIc, SAEs : Consent to End of Study

7 days e-diary

Screening 

Philippines & Africab

Screening 

ROWa

Day -90 Day -28 Day 1 Day 7 Day 28 Variable Duration Delivery 6-Months Post Delivery

RTI surveillance : All MA-RTI Events Captured as Endpoints from Vaccination to End of Study

Pre-Screening

Pre-vaccination 

Vaccination

Visit 1

1-Month Follow-up

Visit 2

Labor & Delivery

Visit 3

Maternal Follow-Up

Visit 4
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AEs for 28 Days

Infant Efficacy, Immunogenicity & Safety Assessment Timeline

AESI, SAEs and NDCMCs: Birth to End of Study

Birth Day 1 28 Days After 6-mo 12-Mo 24-Mo

Delivery & Infant RTI Surveillance Period* 

*Starts 72 hours after delivery

18-Mo

Visit 1 Visit 2 Visit 3

12-Mo Follow-up 

for All Infants 

24-mo Follow-up for Infants 

Born in Study-year 1

Cord 

Blood

Weekly contact with mother / 

RTI site visit + nasal swabs for MA-RTI

Monthly contact with mother / RTI hospitalization 

& severe LRTI requires RTI visit + nasal swabs

RTI Surveillance (e-dairy)

Visit 4 Visit 5 Visit 6

AESI (AE of Special Interest including preterm birth, low birth weight, developmental delay, and asymptomatic SARS-CoV-2 test positive)

SAE (Serious Adverse Event)

NDCMC (Newly Diagnosed Chronic Medical Condition)
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a. N = number of participants in the specified vaccine group. This value is the denominator for the percentage calculations. 

b. n = Number of participants in the specified category. 

Demographic Characteristics

(Maternal Safety Population)

RSVpreF 120 μg

(Na=3682); n (%)

Placebo

(Na=3675); n (%)

Total

(Na=7357); n (%)

Race

White 2383 (64.7) 2365 (64.4) 4748 (64.5)

Black or African American 720 (19.6) 723 (19.7) 1443 (19.6)

Asian 454 (12.3) 464 (12.6) 918 (12.5)

American Indian or Alaskan Native 38 (1.0) 37 (1.0) 75 (1.0)

Native Hawaiian or Other Pacific Islander 9 (0.2) 12 (0.3) 21 (0.3)

Multiracial 30 (0.8) 21 (0.6) 51 (0.7)

Ethnicity

Hispanic/Latino 1049 (28.5) 1075 (29.3) 2124 (28.9)
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*Average GA at vaccination = 30 weeks

Note: One participant is counted under ≥24 weeks to <28 weeks however actual age was 23 weeks 6 days. 

a. N = number of participants in the specified vaccine group. This value is the denominator for the percentage calculations. 

b. n = Number of participants in the specified category. 

Demographic Characteristics (continued 2/2)

(Maternal Safety Population)

RSVpreF 120 μg

(Na=3682); n (%)

Placebo

(Na=3675); n (%)

Total

(Na=7357); n (%)

Age at Vaccination (years)

N 3682 3675 7357

Mean (SD) 29.1 (5.64) 29.0 (5.74) 29.0 (5.69)

Median (Range) 29.0 (16–45) 29.0 (14–47) 29.0 (14–47)

Gestational Age (GA) at Vaccination*

≥24 weeks to <28 weeks 941 (25.6) 909 (24.7) 1850 (25.1)

≥28 weeks to <32 weeks 1085 (29.5) 1128 (30.7) 2213 (30.1)

≥32 weeks to ≤36 weeks 1653 (44.9) 1632 (44.4) 3285 (44.7)

>36 weeks 3 (<0.1) 6 (0.2) 9 (0.1)
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Demographic Characteristics 

(Infant Safety Population)

RSVpreF 120 μg

(Na=3568); n (%)

Placebo

(Na=3558); n (%)

Total

(Na=7126); n (%)

Sex

Male 1816 (50.9) 1793 (50.4) 3609 (50.6)

Female 1752 (49.1) 1765 (49.6) 3517 (49.4)

Race

White 2294 (64.3) 2284 (64.2) 4578 (64.2)

Black or African American 687 (19.3) 688 (19.3) 1375 (19.3)

Asian 420 (11.8) 430 (12.1) 850 (11.9)

American Indian or Alaskan Native 42 (1.2) 36 (1.0) 78 (1.1)

Native Hawaiian or other Pacific Islander 13 (0.4) 11 (0.3) 24 (0.3)

Multiracial 65 (1.8) 59 (1.7) 124 (1.7)

Ethnicity

Hispanic/Latino 1033 (29.0) 1039 (29.2) 2072 (29.1)

a. N = number of participants in the specified vaccine group. This value is the denominator for the percentage calculations. 

b. n = Number of participants in the specified category. 
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Phase 3 Study Objectives

Safety

• Describe the safety profile of RSVpreF

Local reactions and systemic events within 7 days post-vaccination

AEs through 1-month post-vaccination (Maternal)

AEs through 1-month after birth (Infant)

AESIs, SAEs (Maternal and Infant) and NDCMCs (Infant) throughout study

Efficacy

Primary • Prevention of RSV MA-LRTI within 180 days after birth 

• Prevention of RSV severe MA-LRTI within 180 days after birth

Secondary

• Prevention of RSV MA-LRTIs within 360 days after birth

• Prevention of RSV hospitalization within 360 days after birth

• Prevention of MA-LRTIs due to any cause within 360 days after birth

AE, adverse event; AESI, adverse event of special interest; NDCMC, newly diagnosed chronic medical condition; SAE, serious adverse event;

MA, medically attended; LRTI, lower respiratory tract illness; RSV, respiratory syncytial virus
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7.2%

0.2%

6.2%

0.2%

40.6%

10.1%

0

10

20

30

40

50

60

70

80

90

100

RSVpreF

120μg

Placebo RSVpreF

120μg

Placebo RSVpreF

120μg

Placebo

% of Subjects

Vaccine Group (as Administered)

 Mild Moderate Severe

Local Reactions, by Maximum Severity, within 7 Days After Vaccination

Maternal Participants (n=7357)

Erythema/Redness Induration/Swelling Pain at Injection Site
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2.6% 2.9%

46.1% 43.8%

31.0% 27.6%

20.0% 19.2%

26.5%

17.1%

11.6% 10.5% 7.8% 7.0%

11.2% 11.5%

0

10

20

30

40

50

60

70

80

90

100

RSVpreF

120μg

Placebo RSVpreF

120μg

Placebo RSVpreF

120μg

Placebo RSVpreF

120μg

Placebo RSVpreF

120μg

Placebo RSVpreF

120μg

Placebo RSVpreF

120μg

Placebo RSVpreF

120μg

Placebo

% of Subjects

Vaccine Group (as Administered)

Mild or 38.0°C to 38.4°C Moderate or 38.5°C to 38.9°C Severe or 39.0°C to 40.0°C >40°C

Systemic Events, by Maximum Severity, Within 7 Days After Vaccination

Maternal Participants (n=7357)

Fever Fatigue Headache Nausea Muscle Pain Joint Pain Vomiting Diarrhea
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Abbreviations: AESIs = adverse events of special interest; NDCMCs = newly diagnosed chronic medical conditions.

Notes: The severity of the event is in the determination of the investigator. Per statistical analysis plan, 1 month after birth or 1 month after vaccination reflects a 30-day period. However, as per protocol, non-serious adverse events were only solicited

through 28 days after birth/vaccination. AESIs and SAEs were solicited throughout the study for maternal participants.

a. N = number of participants in the specified vaccine group. This value is the denominator for the percentage calculations. b. n = Number of participants reporting at least 1 occurrence of the specified adverse event. For "any event", n = number of 

participants reporting at least 1 occurrence of any adverse event. c. Exact 2-sided confidence interval (CI) calculated using the Clopper and Pearson method. d. An immediate AE is defined as any AE that occurred within the first 30 minutes after 

administration of the investigational product for maternal participants.

Number (%) of Participants Reporting Adverse Events by Category

Within 1 Month After Vaccination

Maternal Participantsa,b,c

13.8

4.2

<0.1 1.7 0.5 0.4 2.7 0.0

13.1

3.7

<0.1 1.3 0.3 0.2 2.5 0.0

0

10

20

30

40

50

60

70

80

90

100

Any AE Serious AE Immediate AEd Severe AE Life-threatening

AE

Related AESIs AE Leading to

Withdrawal

Participants

Reporting ≥ AE %

RSVpreF 120 μg

(N=3682)

Placebo

(N=3675)
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Abbreviations: AESIs = adverse events of special interest; NDCMCs = newly diagnosed chronic medical conditions.

Notes: The severity of the event is in the determination of the investigator. Per statistical analysis plan, 1 month after birth or 1 month after vaccination reflects a 30-day period. However, as per protocol, non-serious adverse events were only solicited

through 28 days after birth/vaccination. AESIs and SAEs were solicited throughout the study for maternal participants.

a. N = number of participants in the specified vaccine group. This value is the denominator for the percentage calculations. b. n = Number of participants reporting at least 1 occurrence of the specified adverse event. For "any event", n = number of 

participants reporting at least 1 occurrence of any adverse event. c. Exact 2-sided confidence interval (CI) calculated using the Clopper and Pearson method. d. An immediate AE is defined as any AE that occurred within the first 30 minutes after 

administration of the investigational product for maternal participants.

Number (%) of Participants Reporting Adverse Events by Category

Within 1 Month After Birth

Infant Participantsa,b,c

37.1

15.5

4.5 1.0 <0.1

8.4

4.8

0.2 0.0

34.5

15.2

3.8 1.0 0.0

7.2 5.9

0.2 0.0

0

10

20

30

40

50

60

70

80

90

100

Any AE Serious AE Severe AE Life-threatening

AE

Related AESIs Congenital

Anomalies

NDCMCs AE Leading to

Withdrawal

Participants

Reporting ≥ AE %

RSVpreF 120 μg

(N=3568)

Placebo

(N=3558)
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Birth Outcomes and Developmental Delay – Infant Participants

Infant Participants with Prematurity, Low Birth Weight, or Developmental Delay (Adverse Events of Special Interest)

0.6

5.6

0.1

5.1

0.3 0.3

4.7

0.2

4.4

0.3

0

10

20

30

40

50

60

70

80

90

100

Early Premature 

≤ 34 weeks

Total Premature 

≤ 37 weeks

Very Low Birth Weight

< 1500g

Low Birth Weight

<2500g

Developmental Delay

% Participants

RSVpreF

(N=3568)

Placebo

(N=3558)
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Deaths and Fetal Losses Reported in the Trial (all unrelated)

Event Type

RSVpreF 120 μg

(N=3682)

Placebo

(N=3675)

Maternal Death: n = 1

• 1 in a maternal participant who received RSVpreF Maternal Death 1 (<0.1%) 0

Fetal Demise: n = 18

• 18 fetal demises in maternal participants who received 

Vaccine/Placebo Fetal death or stillbirth 10 (0.3%) 8 (0.2%)

Event Type

RSVpreF 120 μg

(N=3568)

Placebo

(N=3558)

Infant Death: n = 17

• 16 due to various causes 

• 1 infant adjudicated “Acute Respiratory Illness due to RSV” 

(placebo group)

Infant Death 5 (0.1%) 12 (0.3%)
Breakthroughs that change patients’ lives 199

MATISSE 

Infant Efficacy Endpoints
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C3671008: https://clinicaltrials.gov/ct2/show/NCT04424316?term=C3671008&draw=2&rank=1

Phase 3 Efficacy Endpoints Defined

Primary Endpoints Criteria

Medically attended 

RSV LRTI

Medically attended visit and ≥1: 

• tachypnea (RR ≥60 (<2 m [60 days]) or ≥50 (≥2 to 12 m)

• peripheral capillary oxygen saturation (SpO2) measured in room air <95% 

• chest wall indrawing

Medically attended 

severe RSV LRTI

Medically attended visit and ≥1: 

• tachypnea (RR ≥70 (<2 m [60 days]) or ≥60 (≥2 to 12 m)

• SpO2 measured in room air <93%

• high-flow nasal cannula or mechanical ventilation

• ICU admission for >4 hours; unresponsive/unconscious

Positive 

validated 

RT-PCR

in central 

laboratory

Weekly active surveillance for ARI symptoms

Symptoms trigger nasal swab and possibly a visit

Medically attended visit: Infant participant taken to or seen by a healthcare provider (e.g. outpatient or inpatient visit, emergency room, urgent care, or home visit)

LRTI: Lower respiratory tract illness; SpO2: peripheral capillary oxygen saturation 
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RSV-Positive MA-LRTI

Time Interval Number of Cases (%) Number of Cases (%) Vaccine Efficacyb (%) (CI*)

90 Days after birth 24 (0.7) 56 (1.6) 57.1 (14.7, 79.8)

120 Days after birth 35 (1.0) 81 (2.3) 56.8 (31.2, 73.5)

150 Days after birth 47 (1.3) 99 (2.8) 52.5 (28.7, 68.9)

180 Days after birth 57 (1.6) 117 (3.4) 51.3 (29.4, 66.8)

Maternal Vaccine Group (as Randomized)

RSV-Positive Severe MA-LRTI RSVpreF 120 μg

(Na=3495)

Placebo

(Na=3480)

Time Interval Number of Cases (%) Number of Cases (%) Vaccine Efficacyb (%) (CI*)

90 Days after birth 6 (0.2) 33 (0.9) 81.8 (40.6, 96.3)

120 Days after birth 12 (0.3) 46 (1.3) 73.9 (45.6, 88.8)

150 Days after birth 16 (0.5) 55 (1.6) 70.9 (44.5, 85.9)

180 Days after birth 19 (0.5) 62 (1.8) 69.4 (44.3, 84.1)

Vaccine Efficacy by Cumulative Days after Birth for Two Primary Endpoints

*99.5% CI for 90 days, 97.58% CI for 120/150/180 days. CI LB >20% for all time points.

Abbreviations: RSV = respiratory syncytial virus. a. N = number of participants (at risk) in the specified group. These values are used as the denominators for the percentage calculations. b. Vaccine efficacy was 

calculated as 1-(P/[1-P]), where P is the number of cases in the RSVpreF group divided by the total number of cases. The confidence interval was adjusted using Bonferroni procedure and accounting for the primary 

endpoints results.

Primary Endpoints:
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Abbreviations: MA-LRTI = medically attended lower respiratory tract illness; RSV = respiratory syncytial virus.

a. N = number of participants (at risk) in the specified group. These values are used as the denominators for the percentage calculations.

b. Vaccine efficacy was calculated as 1-(P/[1-P]), where P is the number of cases in the RSVpreF group divided by the total number of cases. The confidence interval was adjusted using Bonferroni procedure and accounting for the primary endpoints results.

Secondary Endpoint: RSV-Positive MA-LRTIs within 360 Days After Birth

Maternal Vaccine Group (as Randomized)

RSVpreF 120 μg

(Na=3495)

Placebo

(Na=3480)

Time Interval Number of Cases (%) Number of Cases (%) Vaccine Efficacyb (%) (99.17% CI)

210 Days after birth 70 (2.0) 127 (3.6) 44.9 (17.9, 63.5)

240 Days after birth 76 (2.2) 133 (3.8) 42.9 (16.1, 61.6)

270 Days after birth 82 (2.3) 137 (3.9) 40.1 (13.0, 59.2)

360 Days after birth 92 (2.6) 156 (4.5) 41.0 (16.2, 58.9)

RSV-Positive MA-LRTIs Occurring Within 360 Days After Birth Met Statistical Criteria for Success 

(CI LB>0%)
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Maternal Vaccine Group (as Randomized)

RSVpreF 120 μg

(Na=3495)

Placebo

(Na=3480)

Time Interval Number of Cases (%) Number of Cases (%) Vaccine Efficacyb (%) (99.17% CI)

90 Days after birth 10 (0.3) 31 (0.9) 67.7 (15.9, 89.5)

180 Days after birth 19 (0.5) 44 (1.3) 56.8 (10.1, 80.7)

360 Days after birth 38 (1.1) 57 (1.6) 33.3 (-17.6, 62.9)

Abbreviations: EAC = endpoint adjudication committee; RSV = respiratory syncytial virus.

a. N = number of participants (at risk) in the specified group. These values are used as the denominators for the percentage calculations.

b. Vaccine efficacy was calculated as 1-(P/[1-P]), where P is the number of cases in the RSVpreF group divided by the total number of cases. The confidence interval was adjusted using Bonferroni procedure and accounting for the primary endpoints results.

Secondary Endpoint: Hospitalizations Due to RSV within 360 Days 

After Birth

Hospitalizations Due to RSV through 180 days Met Statistical Criteria for Success (CI LB>0%)
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Abbreviations: EAC = endpoint adjudication committee; MA-RTI = medically attended respiratory tract illness; RSV = respiratory syncytial virus.

a. N = number of participants (at risk) in the specified group. These values are used as the denominators for the percentage calculations.

b. Vaccine efficacy was calculated as 1-(P/[1-P]), where P is the number of cases in the RSVpreF group divided by the total number of cases.

Exploratory Endpoint: RSV-Positive MA-RTIs (EAC confirmed) within 

180 Days After Birth

Maternal Vaccine Group (as Randomized)

RSVpreF 120 μg

(Na=3495)

Placebo

(Na=3480)

Time Interval Number of Cases (%) Number of Cases (%) Vaccine Efficacyb (%) (95% CI)

90 Days after birth 67 (1.9) 110 (3.2) 39.1 (16.7, 55.7)

180 Days after birth 157 (4.5) 253 (7.3) 37.9 (24.0, 49.5)

RSV-Positive MA-RTIs through 180 Days After Birth
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Consistent efficacy Was Observed Across RSV Subgroup A and B*

RSV Severe MA-LRTI

90, 180 Days

RSV MA-LRTI

90, 180 Days

90 Days

180 Days

90 Days

180 Days

Case Split

(RSVpreF/Placebo) VE

6:33 81.8%

4:8 50.0%

2:25 92.0%

19:62 69.4%

7:14 50.0%

11:44 75.0%

Case Split

(RSVpreF/Placebo) VE

24:56 57.1%

8:12 33.3%

17:43 60.5%

57:117 51.3%

19:26 26.9%

38:87 56.3%

Vaccine Efficacy (%) (95% CI)

Vaccine Efficacy (%) (95% CI)

-100 -50 0 50 100

RSV-B

RSV-A

Overall

RSV-B

RSV-A

Overall

-100 -50 0 50 100

RSV-B

RSV-A

Overall

RSV-B

RSV-A

Overall

* Exploratory Endpoint – no prespecified criterion for RSV A and B
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RSVpreF Efficacious Against Severe Infant MA-LRTI in Phase 3 with a 

Favorable Safety Profile

RSV = Respiratory Syncytial Virus; IA: Interim Analysis; MATISSE: MATernal Immunization Study for Safety and Efficacy; MA-LRTI: Medically Attended Lower Respiratory Tract Illness; CI: Confidence Interval; 

DMC: Data Monitoring Committee; BLA: Biologics License Application; FDA: Food and Drug Administration

Source: Pfizer Press release, Oct 31, 2022

Time Period Vaccine Efficacy

First 90 days of life* 81.8% (CI: 40.6%, 96.3%)

Six-month follow-up* 69.4% (CI: 44.3%, 84.1%)

Time Period Vaccine Efficacy

First 90 days of life* 57.1% (CI: 14.7%, 79.8%)

Six-month follow-up* 51.3% (CI: 29.4%, 66.8%)

Primary Endpoint: Severe MA-LRTI 

Primary Endpoint: MA-LRTI 

RSVpreF investigational vaccine was well-tolerated with a favorable benefit-risk profile for the 

maternal populations and their newborns.

*Confidence intervals are 99.5% CI at 90 days and 97.58% CI at later intervals.
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Worldwide Research, Development and Medical

Vaccine Research and Development

• The participants and their families

• The study investigators, nurses, coordinators, and laboratory personnel

• Pfizer essential colleagues and our vendors

Thanks to