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CompletedNCT06151288Updated Jul 28, 2025Results posted

Safety, Tolerability, and Immunogenicity Study of a 31-Valent Pneumococcal Conjugate Vaccine (VAX-31) in Adults

A Phase 1/2 interventional study of 31 valent pneumococcal conjugate vaccine and 20 valent pneumococcal conjugate vaccine in Pneumococcal Vaccines, sponsored by Vaxcyte, Inc.. Completed at 25 sites in United States. Open to participants aged 50 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-07-28.

Sponsored by Vaxcyte, Inc. · Phase 1/2, Interventional, and Prevention

Phase
Phase 1/2
Study type
Interventional
Enrollment
1,015
Allocation
Randomized
Ages
50 Years and older
Sex
All
01

Study summary

The objective of the study is to evaluate the safety, tolerability and immunogenicity of a single injection of VAX-31 at 3 dose levels compared to Prevnar 20™ (PCV20) in adults 50 to 64 years of age in Stage 1. Stage 2 will evaluate the safety, tolerability, and immunogenicity of a single injection of VAX-31 at 3 dose levels compared to PCV20 in adults aged 50 years and older.

02

Conditions studied

  • Pneumococcal Vaccines
03

In context

Lead sponsor

Vaxcyte, Inc. is the lead sponsor of 9 studies on the registry; 1 is open to participants now.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
50 Years and older
Sexes eligible
All
Accepts healthy volunteers
Yes

Inclusion criteria

  1. Male or female aged 50 to 64 years (inclusive) for Stage 1, or 50 years and older (inclusive) for Stage 2 at the time of randomization into the study.
  2. Able and willing to complete the informed consent process.
  3. Available for clinical follow-up through the last study visit at 6 months after the study vaccination.
  4. In good general health as determined by medical history, vital signs, physical examination, and clinical judgment of the Investigator.
  5. Willing to have blood samples collected, stored indefinitely, and used for research purposes.
  6. Able to provide proof of identity to the satisfaction of the study staff completing the enrollment process.
  7. Women of childbearing potential, defined as premenopausal females capable of becoming pregnant, must have a negative urine pregnancy test immediately prior to randomization and agree to use acceptable contraception
  8. Able to access and use a smartphone, tablet, computer, or other device connected to Wi-Fi or cellular network for completion of an electronic diary.

Exclusion criteria

Exclusion Criteria:

  1. Previous pneumococcal disease (either confirmed or self-reported).
  2. Previous receipt of a licensed or investigational pneumococcal vaccine.
  3. Receipt of any investigational study product within 30 days prior to enrollment into the study, currently participating in another interventional investigational study, or having plans to receive another investigational product(s) while on study.
  4. Planned or actual administration of any licensed vaccine during the period starting 30 days before enrollment into the study through Month 1.
  5. Physical examination indicating any clinically significant medical condition.
  6. Body Temperature >38.0°C (>100.4°F) or acute illness within 3 days prior to study vaccination (subject may be rescheduled).
  7. Previous or existing diagnosis of HIV, Hepatitis B, or Hepatitis C.
  8. History of severe allergic reaction with generalized urticaria, angioedema, or anaphylaxis.
  9. Female who is pregnant, breastfeeding, or planning to become pregnant during study participation.
  10. Bleeding disorder diagnosed by a doctor (e.g., factor deficiency, coagulopathy, or platelet disorder requiring special precautions) resulting in clinically significant bruising or bleeding difficulties with IM injections or blood draws.
  11. Any other chronic or clinically significant medical condition that, in the opinion of the Investigator, would jeopardize the safety or rights of the subject or confound evaluation of the study vaccine.
  12. Any medical, psychiatric, or social condition that in the judgment of the Investigator is a contraindication to protocol participation or impairs a subject's ability to give informed consent.
  13. Received blood or blood product (including Immune Globulin IV) within 90 days prior to enrollment into the study.

  14. Received systemic corticosteroids (except for inhaled, topical, intra-articular) for

    ≥14 consecutive days and has not completed treatment ≤30 days prior to enrollment into the study.

  15. Receiving immunosuppressive therapy.
  16. History of malignancy ≤5 years before enrollment, except for adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer
05

Study design

Phase
Phase 1 / Phase 2
Primary purpose
Prevention
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Quadruple (Participant, Care provider, Investigator, Outcomes assessor)
Enrollment
1,015 participants (actual)

Study arms

  • Experimental
    Group 1

    Participants received a single low dose of VAX-31 administered as an intramuscular injection at Day 1. 1.1 mcg for all serotypes with the exception of serotypes 1, 5, and 22F which is 1.65 mcg.

    Biological: 31 valent pneumococcal conjugate vaccine

  • Experimental
    Group 2

    Participants received a single mid dose of VAX-31 administered as an intramuscular injection at Day 1. 2.2 mcg for all serotypes with the exception of serotypes 1, 5, and 22F which is 3.3 mcg.

    Biological: 31 valent pneumococcal conjugate vaccine

  • Experimental
    Group 3

    Participants received a single high dose of VAX-31 administered as an intramuscular injection at Day 1. 3.3 mcg for all serotypes with the exception of serotypes 1, 5, and 22F which is 4.4 mcg.

    Biological: 31 valent pneumococcal conjugate vaccine

  • Active comparator
    Group 4

    Participants received a single intramuscular injection of the standard dose of PCV20 at Day 1.

    Biological: 20 valent pneumococcal conjugate vaccine

Interventions

  • Biological31 valent pneumococcal conjugate vaccine

    0.5 ml dose of VAX-31 was administered into the deltoid muscle at Day 1

  • Biological20 valent pneumococcal conjugate vaccine

    0.5 ml dose of PCV20 was administered into the deltoid muscle at Day 1

    Also known as: PCV20, Prevnar 20™

06

What researchers measure

Primary outcomes

  1. Percentage of Subjects Reporting Solicited Local Reactions Within 7 Days After Vaccination (Redness, Swelling, and Pain at Injection Site) in Each Age Group

    Solicited local reactions include redness/erythema, swelling/induration, and pain at injection site within 7 days after vaccination in each age group.

    Time frame: 7 days after vaccination

  2. Percentage of Subjects Reporting Solicited Systemic Events Within 7 Days After Vaccination (Fever, Headache, Fatigue, Muscle Pain, and Joint Pain) in Each Age Group Vaccination in Each Age Group

    Solicited systemic reactions include fever, headache, fatigue, muscle pain, and joint pain.

    Time frame: 7 days after vaccination

  3. Percentage of Subjects Reporting Unsolicited Adverse Event in Each Age Group

    Percentage of participants in each age group with adverse events (AEs) whose date of onset occurs after the study vaccine and within the 1 month after vaccination.

    Time frame: 1 month after vaccination

  4. Percentage of Subjects Reporting Serious Adverse Event

    Percentage of participants with SAEs.

    Time frame: 6 months after vaccination

  5. Percentage of Subjects Reporting New Onset of Chronic Illness

    Percentage of participants with NOCIs

    Time frame: 6 months after vaccination

  6. Percentage of Subjects Reporting Medically Attended Adverse Event

    Percentage of participants with MAAEs.

    Time frame: 6 months after vaccination

Secondary outcomes

  1. Percentage of Subjects With Adverse Events Due to Clinically Significant Laboratory Values

    Laboratory values that resulted in treatment and reporting as adverse events 1 month following vaccination.

    Time frame: 1 month after vaccination

  2. Percentage of Participants With a Shift From Normal at Baseline to Abnormal at Post-vaccination in Safety Laboratory Parameters (Hematology, Clinical Chemistry, Urinalysis)

    Shifts from Normal at Baseline to Abnormal on Month 1 (30 days after vaccination) in Hematology, Clinical Chemistry and Urinalysis Parameters Occurring in Subjects Aged 50+ Years.

    Time frame: 1 month after vaccination

  3. 31 VAX-31 Pneumococcal Serotype-specific OPA Geometric Mean Titer

    Antibody geometric mean titers as measured by OPA for the 31 pneumococcal serotypes in VAX-31.

    Time frame: 1 month after vaccination

  4. 31 VAX-31 Pneumococcal Serotype-specific IgG Geometric Mean Concentration

    Antibody geometric mean concentrations as measured by IgG for the 31 pneumococcal serotypes in VAX-31.

    Time frame: 1 month after vaccination

07

Results

Posted Jul 28, 2025
Limitations and caveats
Some limitations of this clinical study include the lack of a group, such as 3.3 mcg or 4.4 mcg, for all serotypes, aimed at understanding whether the dose response of polysaccharide can overcome carrier suppression. The relatively low ethnic diversity of participants is also a limitation, which will be addressed in larger phase 3 clinical trials.

Participant flow

First subject was enrolled 08-Nov-2023 and last subject randomized/vaccinated was 10-Jan-2024. Study sites were medical clinics.

Participant flow — Overall Study
MilestoneVAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20
Started255254253253
Completed247247248249
Not completed8754
Withdrew: Lost to follow-up4243
Withdrew: Withdrawal by subject4511

Outcome measures

PrimaryPercentage of Subjects Reporting Solicited Local Reactions Within 7 Days After Vaccination (Redness, Swelling, and Pain at Injection Site) in Each Age Group

Solicited local reactions include redness/erythema, swelling/induration, and pain at injection site within 7 days after vaccination in each age group.

Time frame:
7 days after vaccination
Reported as:
Number · percentage of participants
Percentage of Subjects Reporting Solicited Local Reactions Within 7 Days After Vaccination (Redness, Swelling, and Pain at Injection Site) in Each Age Group
percentage of participantsVAX-31 Low Dose Overall (Age 50+)VAX-31 Mid Dose Overall (Age 50+)VAX-31 High Dose Overall (Age 50+)PCV20 Overall (Age 50+)VAX-31 Low Dose Age 50-59 YearsVAX-31 Mid Dose Age 50-59 YearsVAX-31 High Dose Age 50-59 YearsPCV20 Age 50-59 YearsVAX-31 Low Dose Age 60+ YearsVAX-31 Mid Dose Age 60+ YearsVAX-31 High Dose Age 60+ YearsPCV20 Age 60+ YearsVAX-31 Low Dose Age 65+ YearsVAX-31 Mid Dose Age 65+ YearsVAX-31 High Dose Age 65+ YearsPCV20 Age 65+ Years
Any solicited local AE; Overall, Any Grade66.867.774.360.372.475.076.468.159.358.271.753.763.849.267.944.8
Pain at injection site; Overall, Any Grade66.066.973.559.971.773.675.068.158.358.271.752.962.149.267.943.3
Erythema (redness) at injection site; Overall, Any Grade6.37.57.14.47.610.47.15.24.63.67.13.71.71.73.83.0
Edema (swelling) at injection site; Overall, Any Grade5.57.97.13.66.97.67.15.23.78.27.12.21.75.15.70
PrimaryPercentage of Subjects Reporting Solicited Systemic Events Within 7 Days After Vaccination (Fever, Headache, Fatigue, Muscle Pain, and Joint Pain) in Each Age Group Vaccination in Each Age Group

Solicited systemic reactions include fever, headache, fatigue, muscle pain, and joint pain.

Time frame:
7 days after vaccination
Reported as:
Number · percentage of participants
Percentage of Subjects Reporting Solicited Systemic Events Within 7 Days After Vaccination (Fever, Headache, Fatigue, Muscle Pain, and Joint Pain) in Each Age Group Vaccination in Each Age Group
percentage of participantsVAX-31 Low Dose Overall (Age 50+)VAX-31 Mid Dose Overall (Age 50+)VAX-31 High Dose Overall (Age 50+)PCV20 Overall (Age 50+)VAX-31 Low Dose Age 50-59 YearsVAX-31 Mid Dose Age 50-59 YearsVAX-31 High Dose Age 50-59 YearsPCV20 Age 50-59 YearsVAX-31 Low Dose Age 60+ YearsVAX-31 Mid Dose Age 60+ YearsVAX-31 High Dose Age 60+ YearsPCV20 Age 60+ YearsVAX-31 Low Dose Age 65+ YearsVAX-31 Mid Dose Age 65+ YearsVAX-31 High Dose Age 65+ YearsPCV20 Age 65+ Years
Any solicited systemic AE (any grade)58.561.468.057.164.165.371.459.550.956.463.755.150.054.260.455.2
Fever (any grade)1.21.21.60.81.41.42.10.90.90.90.90.71.71.70.00.0
Fatigue (any grade)36.836.246.238.940.040.349.337.132.430.942.540.431.028.841.538.8
Headache (any grade)32.031.933.226.635.237.534.330.227.824.531.923.522.423.726.423.9
Muscle pain (any grade)41.946.954.941.349.051.457.141.432.440.952.241.232.842.449.140.3
Joint pain (any grade)17.422.023.316.717.925.722.914.716.717.323.918.420.716.920.817.9
PrimaryPercentage of Subjects Reporting Unsolicited Adverse Event in Each Age Group

Percentage of participants in each age group with adverse events (AEs) whose date of onset occurs after the study vaccine and within the 1 month after vaccination.

Time frame:
1 month after vaccination
Reported as:
Number · percentage of participants
Percentage of Subjects Reporting Unsolicited Adverse Event in Each Age Group
percentage of participantsVAX-31 Low Dose Overall (Age 50+)VAX-31 Mid Dose Overall (Age 50+)VAX-31 High Dose Overall (Age 50+)PCV20 Overall (Age 50+)VAX-31 Low Dose Age 50-59 YearsVAX-31 Mid Dose Age 50-59 YearsVAX-31 High Dose Age 50-59 YearsPCV20 Age 50-59 YearsVAX-31 Low Dose Age 60+ YearsVAX-31 Mid Dose Age 60+ YearsVAX-31 High Dose Age 60+ YearsPCV20 Age 60+ YearsVAX-31 Low Dose Age 65+ YearsVAX-31 Mid Dose Age 65+ YearsVAX-31 High Dose Age 65+ YearsPCV20 Age 65+ Years
Percentage of Subjects Reporting Unsolicited Adverse Event in Each Age Group16.516.918.616.618.416.722.918.113.917.313.315.317.218.613.214.9
PrimaryPercentage of Subjects Reporting Serious Adverse Event

Percentage of participants with SAEs.

Time frame:
6 months after vaccination
Reported as:
Number · percentage of participants
Percentage of Subjects Reporting Serious Adverse Event
percentage of participantsVAX-31 Low Dose Overall (Age 50+)VAX-31 Mid Dose Overall (Age 50+)VAX-31 High Dose Overall (Age 50+)PCV20 Overall (Age 50+)VAX-31 Low Dose Age 50-59 YearsVAX-31 Mid Dose Age 50-59 YearsVAX-31 High Dose Age 50-59 YearsPCV20 Age 50-59 YearsVAX-31 Low Dose Age 60+ YearsVAX-31 Mid Dose Age 60+ YearsVAX-31 High Dose Age 60+ YearsPCV20 Age 60+ YearsVAX-31 Low Dose Age 65+ YearsVAX-31 Mid Dose Age 65+ YearsVAX-31 High Dose Age 65+ YearsPCV20 Age 65+ Years
Percentage of Subjects Reporting Serious Adverse Event0.81.22.01.21.40.72.10.00.01.81.82.20.01.73.83.0
PrimaryPercentage of Subjects Reporting New Onset of Chronic Illness

Percentage of participants with NOCIs

Time frame:
6 months after vaccination
Reported as:
Number · percentage of participants
Percentage of Subjects Reporting New Onset of Chronic Illness
percentage of participantsVAX-31 Low Dose Age 50+ YearsVAX-31 Mid Dose Age 50+ YearsVAX-31 High Dose Age 50+ YearsPCV20 Age 50+ YearsVAX-31 Low Dose Age 50-59 YearsVAX-31 Mid Dose Age 50-59 YearsVAX-31 High Dose Age 50-59 YearsPCV20 Age 50-59 YearsVAX-31 Low Dose Age 60+ YearsVAX-31 Mid Dose Age 60+ YearsVAX-31 High Dose Age 60+ YearsPCV20 Age 60+ YearsVAX-31 Low Dose Age 65+ YearsVAX-31 Mid Dose Age 65+ YearsVAX-31 High Dose Age 65+ YearsPCV20 Age 65+ Years
Percentage of Subjects Reporting New Onset of Chronic Illness0.82.42.02.00.01.42.10.91.93.61.82.93.43.41.91.5
PrimaryPercentage of Subjects Reporting Medically Attended Adverse Event

Percentage of participants with MAAEs.

Time frame:
6 months after vaccination
Reported as:
Number · percentage of participants
Percentage of Subjects Reporting Medically Attended Adverse Event
percentage of participantsVAX-31 Low Dose Overall (Age 50+)VAX-31 Mid Dose Overall (Age 50+)VAX-31 High Dose Overall (Age 50+)PCV20 Overall (Age 50+)VAX-31 Low Dose Age 50-59 YearsVAX-31 Mid Dose Age 50-59 YearsVAX-31 High Dose Age 50-59 YearsPCV20 Age 50-59 YearsVAX-31 Low Dose Age 60+ YearsVAX-31 Mid Dose Age 60+ YearsVAX-31 High Dose Age 60+ YearsPCV20 Age 60+ YearsVAX-31 Low Dose Age 65+ YearsVAX-31 Mid Dose Age 65+ YearsVAX-31 High Dose Age 65+ YearsPCV20 Age 65+ Years
Percentage of Subjects Reporting Medically Attended Adverse Event17.616.513.812.317.018.115.013.818.514.512.410.922.415.39.411.9
SecondaryPercentage of Subjects With Adverse Events Due to Clinically Significant Laboratory Values

Laboratory values that resulted in treatment and reporting as adverse events 1 month following vaccination.

Time frame:
1 month after vaccination
Reported as:
Count of participants · Participants
Percentage of Subjects With Adverse Events Due to Clinically Significant Laboratory Values
ParticipantsVAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20
Hemoglobin (low)0010
Platelets (low)0100
Platelets (high)0010
Leukocytes (low)0001
Leukocytes (high)0000
Alanine aminotransferase (high)1011
Aspartate aminotransferase (high)1010
Cholesterol (high)0100
Creatinine (high)0100
Gamma glutamyl transferase (high)0011
Glucose (low)1000
Glucose (high)1001
Potassium (low)0100
Potassium (high)1000
Sodium (low)0010
Triglycerides (high)1010
Urine glucose0100
Urine hemoglobin1212
Eosinophils0000
Neutrophils0000
Alkaline phosphatase0000
Albumin0000
Bicarbonate0000
Bilirubin0000
Direct bilirubin0000
Calcium0000
Chloride0000
Lactate dehydrogenase0000
Phosphate0000
Protein0000
Urate0000
Urea nitrogen0000
Ketones0000
Leukocyte esterase0000
Urine bilirubin0000
Urine protein0000
Nitrite0000
Urobilinogen0000
SecondaryPercentage of Participants With a Shift From Normal at Baseline to Abnormal at Post-vaccination in Safety Laboratory Parameters (Hematology, Clinical Chemistry, Urinalysis)

Shifts from Normal at Baseline to Abnormal on Month 1 (30 days after vaccination) in Hematology, Clinical Chemistry and Urinalysis Parameters Occurring in Subjects Aged 50+ Years.

Time frame:
1 month after vaccination
Reported as:
Number · percentage of participants
Percentage of Participants With a Shift From Normal at Baseline to Abnormal at Post-vaccination in Safety Laboratory Parameters (Hematology, Clinical Chemistry, Urinalysis)
percentage of participantsVAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20
Eosinophils (10^9/L)1.61.21.60.0
Hemoglobin (g/L)2.81.24.01.2
Neutrophils (10^9/L)5.14.75.12.0
Platelets (10^9/L)1.22.01.20.0
Leukocytes (10^9/L)6.34.74.74.3
Albumin (g/L)0.00.00.00.4
Alkaline phosphatase (U/L)2.41.61.60.8
Alanine aminotransferase (U/L)2.44.32.02.0
Aspartate aminotransferase (U/L)2.02.00.42.4
Bicarbonate (mmol/L)1.22.02.03.2
Direct bilirubin (umol/L)0.80.00.40.0
Bilirubin (umol/L)1.20.80.40.0
Calcium (mmol/L)6.75.97.15.9
Cholesterol (mmol/L)5.16.74.05.5
Chloride (mmol/L)3.13.96.32.4
Creatinine (umol/L)9.05.59.510.3
Gamma glutamyl transferase (U/L)1.62.01.22.0
Glucose (mmol/L)18.021.321.024.1
Potassium (mmol/L)3.52.82.82.8
Lactate dehydrogenase (U/L)0.40.40.00.4
Phosphate (mmol/L)5.93.25.24.8
Protein (g/L)1.21.61.22.8
Sodium (mmol/L)3.93.14.02.8
Triglycerides (mmol/L)6.79.17.58.7
Urate (umol/L)7.17.96.36.7
Urea nitrogen (mmol/L)7.55.17.58.7
Ketones1.60.80.01.2
Leukocyte esterase6.57.17.88.3
Urine bilirubin1.22.42.01.6
Urine glucose0.80.81.30.8
Urine hemoglobin1.22.42.42.5
Urine protein1.22.02.03.7
Nitrite0.41.22.80.8
Urobilinogen0.00.40.00.0
Secondary31 VAX-31 Pneumococcal Serotype-specific OPA Geometric Mean Titer

Antibody geometric mean titers as measured by OPA for the 31 pneumococcal serotypes in VAX-31.

Time frame:
1 month after vaccination
Reported as:
Geometric mean · mcg/mL
31 VAX-31 Pneumococcal Serotype-specific OPA Geometric Mean Titer
mcg/mLVAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20
1412.94 (346.34 to 492.35)474.22 (397.08 to 566.36)509.76 (426.79 to 608.85)410.32 (343.55 to 490.06)
21984.89 (1687.63 to 2334.51)2158.32 (1830.96 to 2544.21)2376.00 (2016.93 to 2798.99)160.47 (136.23 to 189.01)
3247.34 (215.11 to 284.39)301.19 (261.87 to 346.41)369.12 (320.89 to 424.61)351.45 (305.59 to 404.18)
41909.83 (1697.83 to 2148.29)1923.46 (1708.37 to 2165.64)2204.29 (1957.32 to 2482.43)1909.84 (1696.64 to 2149.82)
5453.32 (366.56 to 560.62)553.68 (446.96 to 685.89)643.83 (519.50 to 797.91)518.71 (418.91 to 642.29)
6A3017.66 (2421.39 to 3760.77)3649.18 (2920.00 to 4560.43)5476.69 (4383.39 to 6842.69)5039.25 (4034.70 to 6293.90)
6B3114.80 (2534.60 to 3827.81)3430.49 (2784.90 to 4225.76)4778.40 (3874.70 to 5892.86)4032.19 (3277.67 to 4960.39)
7C5333.37 (4722.15 to 6023.70)5642.80 (4991.20 to 6379.48)6230.76 (5507.58 to 7048.89)656.15 (578.74 to 743.90)
7F4889.66 (4224.12 to 5660.06)5647.05 (4857.85 to 6540.22)6584.45 (5686.59 to 7624.08)4990.65 (4311.96 to 5776.16)
81614.83 (1399.07 to 1863.87)1943.14 (1680.15 to 2247.28)2329.26 (2010.27 to 2698.88)2077.75 (1798.13 to 2400.84)
9N6245.38 (5374.40 to 7257.52)7075.75 (6082.90 to 8230.66)7924.85 (6808.85 to 9223.76)1484.59 (1274.23 to 1729.67)
9V4709.89 (4015.67 to 5524.13)5572.21 (4748.00 to 6539.50)5353.40 (4560.06 to 6284.77)3700.19 (3153.92 to 4341.07)
10A2718.18 (2272.32 to 3251.53)4553.86 (3800.58 to 5456.44)4715.10 (3936.02 to 5648.37)4849.53 (4052.41 to 5803.44)
11A1130.91 (1061.75 to 1204.58)1101.72 (1033.84 to 1174.07)1147.21 (1076.37 to 1222.72)946.05 (887.55 to 1008.41)
12F1199.57 (968.68 to 1485.49)1389.71 (1119.73 to 1724.78)1658.63 (1335.19 to 2060.42)1382.15 (1115.80 to 1712.08)
143574.38 (3048.13 to 4191.50)4000.68 (3404.71 to 4700.99)4657.38 (3965.48 to 5469.99)4306.60 (3670.73 to 5052.62)
15A8705.55 (7402.46 to 10238.03)9982.41 (8488.71 to 11738.94)10153.26 (8613.07 to 11968.86)2696.64 (2290.66 to 3174.58)
15B2891.81 (2423.77 to 3450.24)3548.99 (2969.28 to 4241.87)3877.44 (3243.71 to 4634.98)2568.68 (2149.28 to 3069.93)
16F7931.81 (6996.40 to 8992.27)9980.42 (8794.73 to 11325.96)11055.25 (9739.33 to 12548.96)2130.17 (1876.88 to 2417.65)
17F2146.39 (1904.03 to 2419.61)2112.12 (1871.11 to 2384.19)2160.76 (1913.48 to 2439.99)405.86 (358.82 to 459.08)
18C1928.40 (1599.06 to 2325.57)2302.99 (1910.36 to 2776.31)2640.00 (2190.27 to 3182.06)1845.17 (1531.20 to 2223.52)
19A4199.53 (3606.89 to 4889.55)4726.99 (4055.05 to 5510.27)5032.82 (4316.05 to 5868.63)4271.98 (3666.77 to 4977.07)
19F1754.37 (1541.08 to 1997.18)1817.82 (1595.18 to 2071.52)2185.14 (1917.00 to 2490.78)1321.85 (1160.51 to 1505.61)
20B9756.59 (8193.85 to 11617.39)10664.95 (8936.58 to 12727.60)9988.69 (8381.50 to 11904.07)427.17 (358.03 to 509.66)
22F7196.50 (6125.39 to 8454.92)8843.18 (7517.43 to 10402.73)8633.65 (7333.92 to 10163.72)9989.08 (8496.59 to 11743.74)
23A2778.60 (2235.23 to 3454.05)2929.12 (2354.16 to 3644.51)3253.49 (2612.93 to 4051.07)175.01 (139.54 to 219.49)
23B1919.13 (1555.79 to 2367.32)1855.53 (1501.21 to 2293.47)2010.19 (1625.78 to 2485.48)248.33 (200.25 to 307.96)
23F1829.26 (1475.00 to 2268.62)2128.26 (1714.84 to 2641.34)2491.49 (2007.55 to 3092.09)1433.09 (1156.18 to 1776.33)
317199.08 (5973.44 to 8676.19)7821.34 (6480.26 to 9439.94)8605.44 (7127.04 to 10390.50)623.66 (515.16 to 755.00)
33F10686.74 (9102.59 to 12546.58)12553.75 (10684.65 to 14749.82)12763.17 (10869.89 to 14986.22)10332.19 (8815.38 to 12109.97)
35B9264.48 (8193.76 to 10475.12)9913.10 (8758.88 to 11219.41)10659.18 (9415.66 to 12066.95)2845.55 (2511.80 to 3223.64)
Secondary31 VAX-31 Pneumococcal Serotype-specific IgG Geometric Mean Concentration

Antibody geometric mean concentrations as measured by IgG for the 31 pneumococcal serotypes in VAX-31.

Time frame:
1 month after vaccination
Reported as:
Geometric mean · mcg/mL
31 VAX-31 Pneumococcal Serotype-specific IgG Geometric Mean Concentration
mcg/mLVAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20
15.56 (4.78 to 6.48)5.55 (4.76 to 6.48)6.40 (5.49 to 7.46)4.32 (3.71 to 5.04)
212.64 (10.60 to 15.08)14.78 (12.37 to 17.66)15.04 (12.59 to 17.97)0.93 (0.78 to 1.11)
30.47 (0.40 to 0.55)0.53 (0.45 to 0.61)0.61 (0.52 to 0.71)0.60 (0.52 to 0.70)
41.22 (1.02 to 1.46)1.56 (1.30 to 1.86)1.73 (1.44 to 2.06)1.50 (1.26 to 1.79)
52.38 (2.01 to 2.83)2.82 (2.38 to 3.35)2.80 (2.36 to 3.33)2.47 (2.08 to 2.93)
6A2.97 (2.42 to 3.66)3.15 (2.56 to 3.89)4.28 (3.48 to 5.27)3.14 (2.55 to 3.87)
6B3.26 (2.58 to 4.13)3.88 (3.06 to 4.92)5.01 (3.95 to 6.35)3.08 (2.43 to 3.91)
7C11.96 (9.47 to 15.09)14.02 (11.09 to 17.73)13.71 (10.83 to 17.36)0.56 (0.44 to 0.71)
7F5.81 (4.97 to 6.80)6.59 (5.63 to 7.72)7.10 (6.06 to 8.32)5.14 (4.39 to 6.01)
86.13 (5.24 to 7.16)7.44 (6.36 to 8.70)9.69 (8.27 to 11.34)6.99 (5.97 to 8.17)
9N6.52 (5.49 to 7.73)6.60 (5.56 to 7.84)7.92 (6.67 to 9.41)1.00 (0.84 to 1.19)
9V3.77 (3.12 to 4.55)4.31 (3.57 to 5.20)3.78 (3.12 to 4.57)2.63 (2.18 to 3.17)
10A6.67 (5.27 to 8.43)7.55 (5.96 to 9.56)8.21 (6.47 to 10.40)10.82 (8.55 to 13.69)
11A4.78 (4.00 to 5.71)5.70 (4.76 to 6.82)5.37 (4.49 to 6.42)3.75 (3.13 to 4.48)
12F1.52 (1.24 to 1.86)1.96 (1.60 to 2.40)1.70 (1.39 to 2.08)1.38 (1.13 to 1.68)
147.41 (6.02 to 9.12)10.33 (8.38 to 12.74)11.58 (9.38 to 14.28)9.15 (7.42 to 11.27)
15A20.93 (17.27 to 25.38)26.40 (21.75 to 32.06)25.91 (21.32 to 31.50)4.22 (3.48 to 5.12)
15B12.34 (10.04 to 15.16)4.06 (3.45 to 4.79)18.25 (14.82 to 22.46)13.17 (10.71 to 16.19)
16F3.03 (2.57 to 3.57)4.06 (3.45 to 4.79)3.82 (3.24 to 4.51)0.95 (0.81 to 1.12)
17F9.54 (8.08 to 11.27)11.05 (9.35 to 13.06)12.67 (10.72 to 14.99)0.56 (0.47 to 0.66)
18C7.15 (5.91 to 8.67)8.34 (6.87 to 10.11)8.31 (6.85 to 10.09)6.62 (5.46 to 8.03)
19A8.08 (6.64 to 9.83)11.00 (9.03 to 13.39)11.83 (9.71 to 14.41)8.53 (7.01 to 10.38)
19F5.94 (4.82 to 7.34)6.94 (5.62 to 8.58)8.91 (7.20 to 11.02)4.37 (3.54 to 5.40)
20B16.33 (13.89 to 19.19)20.44 (17.37 to 24.05)20.24 (17.20 to 23.83)3.91 (3.33 to 4.60)
22F3.45 (2.93 to 4.06)4.05 (3.43 to 4.77)4.60 (3.90 to 5.43)4.37 (3.71 to 5.16)
23A3.05 (2.43 to 3.84)3.23 (2.57 to 4.07)4.01 (3.18 to 5.05)0.52 (0.42 to 0.66)
23B23.14 (19.65 to 27.27)25.41 (21.54 to 29.97)28.61 (24.25 to 33.76)11.27 (9.56 to 13.29)
23F4.58 (3.79 to 5.53)5.51 (4.56 to 6.66)6.45 (5.33 to 7.80)4.60 (3.81 to 5.56)
316.84 (5.64 to 8.31)10.46 (8.61 to 12.72)11.92 (9.80 to 14.50)0.44 (0.36 to 0.53)
33F13.10 (11.12 to 15.43)14.21 (12.05 to 16.76)15.88 (13.46 to 18.73)12.24 (10.39 to 14.43)
35B25.39 (21.52 to 29.96)31.05 (26.28 to 36.68)36.39 (30.77 to 43.03)3.05 (2.58 to 3.60)

Adverse events

Collected over 6 months. Non-serious events are listed at a 1% frequency threshold.

Adverse event summary by group
GroupDeathsSeriousOther
VAX-31 Low Dose Overall (Age 50+)0/255 (0%)2/255 (0.8%)189/255 (74.1%)
VAX-31 Mid Dose Overall (Age 50+)0/254 (0%)3/254 (1.2%)196/254 (77.2%)
VAX-31 High Dose Overall (Age 50+)0/253 (0%)5/253 (2%)209/253 (82.6%)
PCV20 Overall (Age 50+)0/253 (0%)3/253 (1.2%)178/253 (70.4%)
Most frequent serious events
Showing 10 of 12
Most frequent serious events
EventVAX-31 Low Dose Overall (Age 50+)VAX-31 Mid Dose Overall (Age 50+)VAX-31 High Dose Overall (Age 50+)PCV20 Overall (Age 50+)
PneumoniaInfections and infestations0/2550/2542/2530/253
Gait disturbanceGeneral disorders0/2550/2540/2531/253
Hip fractureInjury, poisoning and procedural complications0/2550/2540/2531/253
OsteoarthritisMusculoskeletal and connective tissue disorders0/2550/2540/2531/253
Cholecystitis acuteHepatobiliary disorders0/2550/2541/2530/253
Hepatic cancerNeoplasms benign, malignant and unspecified (incl cysts and polyps)0/2550/2541/2530/253
AsthmaRespiratory, thoracic and mediastinal disorders0/2550/2541/2530/253
Type 2 diabetes mellitusMetabolism and nutrition disorders0/2551/2540/2530/253
LymphomaNeoplasms benign, malignant and unspecified (incl cysts and polyps)0/2551/2540/2530/253
Deep vein thrombosisVascular disorders0/2551/2540/2530/253
Most frequent other events
Most frequent other events
EventVAX-31 Low Dose Overall (Age 50+)VAX-31 Mid Dose Overall (Age 50+)VAX-31 High Dose Overall (Age 50+)PCV20 Overall (Age 50+)
Pain at injection siteSkin and subcutaneous tissue disorders167/255170/254186/253151/252
Muscle painMusculoskeletal and connective tissue disorders106/255119/254139/253104/252
TirednessGeneral disorders93/25592/254117/25398/252
HeadacheGeneral disorders81/25581/25484/25367/252
Joint painMusculoskeletal and connective tissue disorders44/25556/25459/25342/252
EdemaSkin and subcutaneous tissue disorders14/25520/25418/2539/252
ErythemaSkin and subcutaneous tissue disorders16/25519/25418/25311/252
FeverGeneral disorders3/2553/2544/2532/252
Injection site pruritisGeneral disorders1/2554/2542/2530/253
Nasal congestionRespiratory, thoracic and mediastinal disorders3/2550/2541/2531/253

Baseline characteristics

Age, Continuous
Age, Continuous(years)VAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20Total
Median58.0 (50.0 to 84.0)58.0 (50.0 to 86.0)59.0 (50.0 to 79.0)60.0 (50.0 to 82.0)59.0 (50.0 to 86.0)
Sex: Female, Male
Sex: Female, Male(Participants)VAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20Total
Female151160150148609
Male10494103105406
Ethnicity (NIH/OMB)
Ethnicity (NIH/OMB)(Participants)VAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20Total
Hispanic or Latino43444243172
Not Hispanic or Latino210208209209836
Unknown or Not Reported22217
Race (NIH/OMB)
Race (NIH/OMB)(Participants)VAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20Total
American Indian or Alaska Native23005
Asian354315
Native Hawaiian or Other Pacific Islander00011
Black or African American60555160226
White188191196185760
More than one race00000
Unknown or Not Reported20248
Height (cm)
Height (cm)(cm)VAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20Total
Median167.6 (160.3 to 175.3)169.1 (162.6 to 175.3)168.0 (162.6 to 175.3)167.6 (160.8 to 175.3)167.9 (162.5 to 175.3)
Weight (kg)
Weight (kg)(kg)VAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20Total
Median82.56 (71.10 to 94.30)85.80 (72.00 to 102.15)84.00 (71.90 to 99.79)83.64 (72.12 to 97.52)83.92 (71.90 to 98.80)
Body Mass Index (kg/m^2)
Body Mass Index (kg/m^2)(kg/m^2)VAX-31 Low DoseVAX-31 Mid DoseVAX-31 High DosePCV20Total
Median28.90 (25.98 to 33.47)30.42 (25.58 to 34.42)28.82 (25.60 to 33.37)29.11 (25.91 to 34.14)29.27 (25.78 to 33.91)
08

Study locations

25 sites
  • AMR Mobile
    Mobile, Alabama 36608, United States
  • AMR Phoenix
    Phoenix, Arizona 85282, United States
  • Research Centers of America
    Hollywood, Florida 33024, United States
  • Health Awareness
    Jupiter, Florida 33458, United States
  • Optimal Research
    Melbourne, Florida 32934, United States
  • Precision Clinical Research
    Sunrise, Florida 33351, United States
  • Velocity Clinical Research, Savannah
    Savannah, Georgia 31406, United States
  • Healthcare Research Network II, LLC
    Flossmoor, Illinois 60422, United States
  • Johnson County Clin-Trials
    Lenexa, Kansas 66219, United States
  • DM Clinical Research - Detroit
    Detroit, Michigan 48076, United States
  • Velocity Clinical Research Omaha
    Omaha, Nebraska 68134, United States
  • WR-CRCN
    Las Vegas, Nevada 89106, United States
  • Cenexel AMRI
    Toms River, New Jersey 08755, United States
  • Rochester Clinical Research
    Rochester, New York 14609, United States
  • CTI Clinical Research Center
    Cincinnati, Ohio 45212, United States
  • Velocity Clinical Research, Cleveland
    Cleveland, Ohio 44122, United States
  • DM Clinical Research - Philadelphia
    Philadelphia, Pennsylvania 19107, United States
  • Velocity Clinical Research
    Warwick, Rhode Island 02886, United States
  • Coastal Carolina Research
    North Charleston, South Carolina 29405, United States
  • AMR Knoxville
    Knoxville, Tennessee 37909, United States
  • Benchmark Research
    Fort Worth, Texas 76135, United States
  • Benchmark Research
    San Angelo, Texas 76904, United States
  • CenExel JBR Clinical Research
    Salt Lake City, Utah 84107, United States
  • Charlottesville Medical Research
    Charlottesville, Virginia 22911, United States
  • Health Research of Hampton Roads
    Newport News, Virginia 23606, United States
09

References and documents

Publications

  • Wassil J, Fairman J, Fierro CA, Clark J, Bennett S, Johnson D, Jiang Q, Migone TS, Paschenko A, Simon JK, Lamola S, Sisti M. Safety, tolerability, and immunogenicity of a 31-valent pneumococcal conjugate vaccine (VAX-31) in healthy adults aged 50 years and older from the USA: a phase 1/2, double-blinded, active-controlled, parallel-group, dose-finding randomised clinical trial. Lancet Infect Dis. 2026 Mar 18:S1473-3099(26)00059-9. doi: 10.1016/S1473-3099(26)00059-9. Online ahead of print. PubMed 41864214 ↗

Study documents

  • Study protocol · Dec 8, 2023
  • Statistical analysis plan · Jun 26, 2024

Documents are hosted by the registry — open the source record to download them.

Individual participant data

Plan to share: Yes — Vaxcyte is committed to providing access to anonymized data from the company's clinical trials for the purpose of legitimate scientific research. Requests for data may be addressed to datasharing@vaxcyte.com. Requests must be accompanied by a detailed analysis plan and will be reviewed for scientific validity. Data will be made available after initial product approval. Sharing of data may require execution of a data-sharing agreement.

Supporting information: Study protocol

10

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on Jul 28, 2025, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
11

Registry details

Key details

Study ID
NCT06151288
Lead sponsor
Vaxcyte, Inc.
Responsible party
Sponsor
First posted
Nov 30, 2023
Start date
Nov 8, 2023
Primary completion
Jul 17, 2024
Completion
Jul 17, 2024
Results posted
Jul 28, 2025
Last update
Jul 28, 2025

Study contacts

Clinical Development
study director · Vaxcyte, Inc.

Oversight

Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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