Sanofi posts results of Phase 3 MenACYW conjugate vaccine study in infants
Sanofi Pasteur posted results of a Phase 3 study that compared MenACYW conjugate vaccine with Nimenrix in 840 infants on 2026-10-07. The record lists geometric mean titers and seroresponse for serogroups A, C, W and Y.
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Sanofi posted results of a Phase 3 study that compared MenACYW conjugate vaccine with Nimenrix in healthy infants and toddlers, according to the study record in the public trial registry. The record lists the results as first posted on 2026-10-07. The sponsor is Sanofi Pasteur, a Sanofi Company. The study enrolled 840 participants, and its status is COMPLETED.
Study design and groups
The record says the study was conducted to support a 2-dose series (1+1 vaccination schedule) for immunization of individuals from 6 months of age. The study was designed to evaluate non-inferiority of the immunological response of MenACYW conjugate vaccine to Nimenrix after the 2-dose series. The record also lists the vaccine as MenQuadfi.
Participants were randomized in a 1:1 ratio. The record lists triple masking and describes the study as modified double-blind. Group 1 received MenACYW conjugate vaccine. Group 2 received Nimenrix. Both groups followed the same schedule. Dose 1, the priming dose, was given at 6-7 months of age on Day 1. Dose 2, the booster dose, was given at 12-13 months of age at Month 6. Each dose was a 0.5 mL intramuscular injection.
The record says the study ran at 47 centers in 6 countries. The countries listed are Czechia, Denmark, Finland, Germany, Poland and Romania. The study started on 2024-03-19. The record lists primary completion and completion both as 2025-11-14.
Primary outcomes
The record lists two primary outcomes. The outcomes both use a serum bactericidal assay with human complement (hSBA) 30 days after Dose 2, at Month 7.
The first primary outcome is geometric mean titers (GMTs) against serogroups A, C, W and Y. The record lists these GMTs for MenACYW conjugate vaccine and for Nimenrix:
- Serogroup A: 170 and 203
- Serogroup C: 1112 and 302
- Serogroup Y: 289 and 268
- Serogroup W: 275 and 299
The record says non-inferiority was demonstrated if the lower limit of the 2-sided 95% confidence interval (CI) was greater than 1/1.5 for all four serogroups. The record lists these geometric mean titer ratios with 95% confidence intervals:
- Serogroup A: 0.838 (0.648 to 1.08)
- Serogroup C: 3.68 (3.01 to 4.49)
- Serogroup Y: 1.08 (0.915 to 1.27)
- Serogroup W: 0.922 (0.756 to 1.13)
The second primary outcome is the percentage of participants with vaccine seroresponse 30 days after Dose 2, compared with before Dose 1. The record lists these percentages for MenACYW conjugate vaccine and for Nimenrix:
- Serogroup A: 80.4 and 78.1
- Serogroup C: 98.9 and 96.2
- Serogroup Y: 99.0 and 98.5
- Serogroup W: 97.6 and 97.4
The record says, for this outcome, that non-inferiority was demonstrated if the lower limit of the 2-sided 95% CI was greater than -10% for all four serogroups. The record lists these differences in percentage of participants with 95% confidence intervals:
- Serogroup A: 2.29 (-4.58 to 9.18)
- Serogroup C: 2.69 (-0.03 to 5.83)
- Serogroup Y: 0.42 (-1.74 to 2.77)
- Serogroup W: 0.12 (-2.72 to 3.02)
The analysis fields list the criteria and the intervals. They do not state a conclusion.
Secondary and safety measures
The record lists many secondary outcomes. The outcomes include hSBA and baby rabbit complement (rSBA) titers after Dose 1 and after Dose 2. The percentage of participants with hSBA titers of 1:8 or higher 30 days after Dose 1, on Day 31, is one secondary outcome. The record lists these percentages for MenACYW conjugate vaccine and for Nimenrix:
- Serogroup A: 71.8 and 90.0
- Serogroup C: 99.2 and 89.8
- Serogroup Y: 72.8 and 56.6
- Serogroup W: 50.9 and 24.4
The safety measures cover immediate unsolicited systemic adverse events up to 30 minutes after each vaccination. The measures also cover solicited injection site reactions and systemic reactions up to 7 days after each vaccination, and unsolicited adverse events up to 30 days after each vaccination. The record lists serious adverse events and adverse events of special interest from Day 1 up to 30 days after the last vaccination, approximately 7 months.
Participants and data access
The record lists 422 participants started in Group 1 and 418 in Group 2. The safety analysis set has 417 and 412. A total of 402 participants completed in Group 1 and 393 in Group 2, and 20 and 25 did not complete. The record gives the reasons for Group 1 and Group 2 as follows: lost to follow-up, 2 and 7; withdrawal by parent or guardian, 16 and 6; protocol violation, 2 and 5; adverse event, 0 and 6.
The mean age at enrollment was 6.5 months in both groups (standard deviation 0.50). The record lists 382 female and 458 male participants. The record lists eligible participants as aged 6 to 7 months and healthy. The record excludes infants with earlier vaccination against meningococcal A, C, W or Y disease.
Sanofi lists individual participant data sharing as YES. The record says qualified researchers may request access to patient level data and related study documents, including the clinical study report and the study protocol.