Surveillance of adverse events following immunisation with meningococcal B vaccine (4CMenB), South Australia, 2018-2022.

South Australia (SA)'s ongoing statewide Meningococcal B Vaccination Program (the Program) provides 4CMenB (Bexsero) to children aged six weeks to 12 months, and young people aged 15 to 17 years. This retrospective study aimed to evaluate the safety profile of 4CMenB, using routinely collected data on adverse events following immunisation (AEFI). The study population was all participants in the Program, as well as those who received 4CMenB through the National Immunisation Program (NIP), from the Program's commencement on 1 October 2018 to 30 June 2022. Information about AEFIs was collated and classified according to the Australian Product Information (PI) for 4CMenB and the internal Meningococcal B Immunisation Program Vaccine Safety Plan (the Safety Plan). The total number of 4CMenB vaccines distributed (and not subsequently discarded) during the study period for both the Program and the NIP was 437,462 vaccines. A total of 306 AEFI notifications were received during the study period, equating to a reporting rate of 69.9 notifications per 100,000 doses. Most reported AEFI were known, common, non-serious adverse events (85 % of reports), followed by serious AEFI (13 %) and suspected unexpected serious adverse reactions (SUSAR) (2 %). The most frequently reported non-serious AEFI clinical features were rash (14 %), injection site reaction (14 %), nausea/vomiting/diarrhoea (11 %) and fever (11 %). Of the serious AEFI, the most frequently reported were hypotonic-hyporesponsive events (HHE) (n = 12; 30 %), various problems requiring inpatient hospital admission (n = 10; 25 %), and high fever greater than 40 °C (n = 6; 15 %). There were five episodes of anaphylaxis or anaphylactoid reaction, four episodes of seizure and two episodes of febrile convulsion. No specific new safety signal was ascertained from review of serious AEFI and SUSAR. A high proportion (83 %) of children under two years with reported AEFI were administered prophylactic acetaminophen. Our findings from prolonged, population-based analysis of AEFI complement the existing safety data on the 4CMenB vaccine and may be used to inform the implementation of 4CMenB vaccination programs at scale in other jurisdictions.