221. Immunogenicity and Safety Study of a Quadrivalent Meningococcal Conjugate Vaccine (MenACYW-TT) when Co-administered with Routine Pediatric Vaccines in Healthy Infants and Toddlers in the US and Puerto Rico

Abstract Background The incidence of invasive meningococcal disease (IMD) was 0.09 per 100,000 population in the US in 2022, with the highest rates observed in infants < 1 year of age. MenQuadfi® (MenACYW-TT) is licensed in the US against IMD for individuals 2 years and older and is under development for use from 6 weeks of age to provide protection against IMD caused by serogroups A, C, Y and W. Methods In this modified double-blind, Phase-3 study (NCT03537508), 2627 healthy infants (age ≥ 42 to ≤ 89 days) were randomized 2:1 to receive 4 dose series of MenACYW-TT at 2, 4, 6, and 12-15 months or 15-18 months of age (Group 1), or 4 doses of MenACWY-CRM at 2, 4, 6 and 12 months of age (Group 2). Immunogenicity and safety of MenACYW-TT vs MenACWY-CRM were evaluated when co-administered with routine pediatric vaccines following US schedules. Results The primary and secondary objectives were met: percentage of subjects who achieved hSBA vaccine seroresponse after the 4 dose series (at 2, 4, 6 and 12-15 months of age) was 79.4%, 97.0%, 96.4% and 97.6% for serogroups A, C, Y and W, respectively in Group 1 and was non-inferior to those in Group 2. Seroprotection rates in Group 1 were 77.9%, 99.0%, 98.3% and 98.6%, and non-inferior to Group 2 after 3 doses (at 2, 4 and 6 months of age) for the serogroups A, C, Y and W, respectively; immune responses to co-administered routine pediatric vaccines in infants and toddlers 6 weeks old to 18 months of age were non-inferior between Group 1 and 2. Overall, 2,594 (98.7%) participants had received at least one (any) dose and 2080 (79.2%) received all 4 doses of the study vaccines. Safety profile and tolerance of MenACYW-TT and MenACWY-CRM were comparable. Within 30 minutes of any vaccination, 2 participants (1 in each group) experienced a non-related immediate AE. In Group 1, 99 subjects (5.7%), and in Group 2, 38 subjects (4.4%) reported serious adverse events (SAEs) during the study; 13 subjects in Group 1 (0.8%) and 5 subjects in Group 2 (0.6%) reported an adverse event of special interest (AESI). There were 2 SAEs that lead to study discontinuation, including 1 death. All SAEs, AESIs and deaths were unrelated to the study vaccines (Table 1). Conclusion MenACYW-TT administered with routine pediatric vaccines was immunogenic and safe in healthy infants and toddlers. Disclosures James Campbell, GSK: Contracts with my University to perform vaccine clinical trials|Merck: Contracts with my University to perform vaccine clinical trials|Moderna: Contracts with my University to perform vaccine clinical trials|Pfizer: Contracts with my University to perform vaccine clinical trials|Sanofi: Grant/Research Support|Sanofi: Sanofi supported the writing of the manuscript Betzana Zambrano, MD, Sanofi: Employee|Sanofi: Stocks/Bonds (Public Company) Mandeep S. Dhingra, MD, Sanofi: Employee|Sanofi: Stocks/Bonds (Public Company) Sandeep Gupta, MD, Sanofi: Employee|Sanofi: Stocks/Bonds (Public Company) Lucia Gan, PhD, Sanofi: Employee|Sanofi: Stocks/Bonds (Public Company) Siham Bchir, MSc, Sanofi: Employee|Sanofi: Stocks/Bonds (Public Company) Julie Chaix, n/a, Sanofi: Employee Olga Syrkina, MD, Sanofi: Employee|Sanofi: Stocks/Bonds (Public Company) Julie masson, n/a, Sanofi: Contract Employee Olga Lyabis, MD, Sanofi: Employee|Sanofi: Stocks/Bonds (Public Company) Christine Rehm, MD, Sanofi: Employee|Sanofi: Stocks/Bonds (Public Company)