Short-Term Safety of Concomitant Meningococcal B and National Immunisation Program Vaccines in Infants Aged < 15 Months: A Survey-Based Surveillance Study.

OBJECTIVE: To examine short-term safety outcomes following vaccination at 2-, 4-, 6- and 12-month timepoints, comparing infants receiving meningococcal B (MenB) vaccines concomitantly with National Immunisation Program (NIP) vaccines to those receiving vaccines at separate visits. STUDY TYPE: Observational cohort survey study. SETTING, PARTICIPANTS: Online surveys via AusVaxSafety were sent 3 days post-immunisation to collect reports of adverse events following immunisation (AEFIs). Infants aged < 15 months were included if, between 1 April 2022 and 31 March 2025, they received NIP and MenB vaccines concomitantly or separately at schedule timepoints, and their carer completed an AusVaxSafety survey. MAIN OUTCOME MEASURES: Bayesian multinomial logistic regression estimated the risk of reporting any AEFI, medical review and impact on daily activities following each vaccination strategy. RESULTS: Of 45,215 infants receiving NIP and MenB vaccines at the 2-, 4-, 6- and 12-month timepoints (with or without other vaccines), 72% (32,751/45,215) received concomitant vaccination. Excluding those with additional vaccines, 10,959 were included in the analysis. The adjusted model showed the cumulative risk of any AEFI was lower under the concomitant strategy compared with the separate strategy at 2 months (29% [95% credible interval (CrI), 26% to 31%] vs. 35% [95% CrI, 31% to 40%], risk difference -6.7 [95% CrI, -11.5 to -2.2]) and similar at 4 months (45% [95% CrI, 43% to 48%] vs. 47% [95% CrI, 43% to 52%]), 6 months (45% [95% CrI, 42% to 49%] vs. 44% [95% CrI, 38% to 50%]) and 12 months (47% [95% CrI, 45% to 50%] vs. 52% [95% CrI, 48% to 56%]). Medical review within 3 days was lower at 12 months in the concomitant group (4.1% [95% CrI, 3.4% to 5.0%] vs. separate 6.3% [95% CrI, 4.7% to 8.3%], risk difference -2.2 [-4.3 to -0.4]) and comparable across earlier time points (concomitant 2.3%-4.2% vs. separate 3.6%-3.9%). Impact on daily activities was low (concomitant 1.1%-8.5% vs. separate 1.6%-8.3%) with no differences observed between strategies. CONCLUSIONS: Separating MenB vaccines from routine NIP vaccines does not reduce, and may increase, the cumulative reaction burden across visits. Findings support concomitant administration.