'B Part of It' School Leaver study: a repeat cross-sectional study to assess the impact of increasing coverage with meningococcal B (4CMenB) vaccine on carriage of Neisseria meningitidis

THE ROLE OF SCHOOLS IN MENINGOCOCCAL CARRIAGE AMONG ADOLESCENTS AND YOUNG ADULTS IN SOUTH AUSTRALIA

Neisseria meningitidis carriage peaks in adolescents. This secondary analysis of a randomized controlled trial (NCT03089086) assessing 4CMenB herd protection in South Australia ("B-Part-of-It" study) explored school attributes linked to baseline carriage in 34,489 adolescents prevaccination. Carriage was higher in students attending single-sex [adjusted odds ratio (aOR): 1.49; 95% confidence interval (CI): 1.14-1.93], boarding (aOR: 1.92; 1.13-3.27) and government schools (aOR: 1.32, 1.09-1.61).

Longitudinal study of meningococcal carriage in adolescents and young adults in South Australia 2017-2020

BACKGROUND

This analysis investigated longitudinal changes in meningococcal carriage in adolescents in South Australia over 4 years.

METHODS

Data from the "B Part of It" study, which included a state-wide cluster randomized controlled trial in secondary-school students (n = 34,489 in 2017 and 2018) and serial cross-sectional studies in school leavers aged 17-25 years (n = 4028 in 2019-2020). Individuals had oropharyngeal swabs collected annually. This study included two unique cohorts: (1) individuals enrolled in 2019, with three consecutive annual swabs taken in 2017, 2018 and 2019; and (2) individuals enrolled in 2020, with swabs taken in 2017, 2018, and 2020. Disease-associated N. meningitidis genogroups were identified using PCR and whole genome sequencing. Univariate analysis identified risk factors for recurrent carriage (≥2).

RESULTS

Among school leavers, 50 (1.7%, total n = 2980) had carriage detected at successive visits. In participants with meningococcal carriage at successive visits, 38/50 (76.0%) had the same genogroup detected by porA PCR. Of those, 19 had the same MLST type and demonstrated minimal variation, indicating they most likely had sustained carriage of the same isolate (range 226 to 490 days, mean duration 352 [SD 51] days). In the 2019 school leaver cohort, 6.7% acquired carriage in their first year out of school compared to 3.3% in their final school year. Compared to single carriage detection, recurrent carriage was potentially more likely in older adolescents (16 compared to ≤15 years; OR = 1.97 (95%CI 1.0, 3.86); p = 0.048).

CONCLUSION

Whilst carriage is typically transient, some adolescents/young adults may have persistent carriage and are likely to be an important group in the transmission of meningococci.

Geographical distribution of invasive meningococcal disease and carriage: A spatial analysis

Little information exists concerning the spatial relationship between invasive meningococcal disease (IMD) cases and Neisseria meningitidis (N. meningitidis) carriage. The aim of this study was to examine whether there is a relationship between IMD and asymptomatic oropharyngeal carriage of meningococci by spatial analysis to identify the distribution and patterns of cases and carriage in South Australia (SA). Carriage data geocoded to participants' residential addresses and meningococcal case notifications using Postal Area (POA) centroids were used to analyse spatial distribution by disease- and non-disease-associated genogroups, as well as overall from 2017 to 2020. The majority of IMD cases were genogroup B with the overall highest incidence of cases reported in infants, young children, and adolescents. We found no clear spatial association between N. meningitidis carriage and IMD cases. However, analyses using carriage and case genogroups showed differences in the spatial distribution between metropolitan and regional areas. Regional areas had a higher rate of IMD cases and carriage prevalence. While no clear relationship between cases and carriage was evident in the spatial analysis, the higher rates of both carriage and disease in regional areas highlight the need to maintain high vaccine coverage outside of the well-resourced metropolitan area.

Meningococcal B Immunisation in Adults and Potential Broader Immunisation Strategies: A Narrative Review

Recombinant vaccines against invasive meningococcal disease due to Neisseria meningitidis serogroup B (MenB) have shown substantial impact in reducing MenB disease in targeted populations. 4CMenB targets four key N. meningitidis protein antigens; human factor H binding protein (fHbp), Neisserial heparin binding antigen (NHBA), Neisseria adhesin A (NadA) and the porin A protein (PorA P1.4), with one or more of these expressed by most pathogenic MenB strains, while MenB-FHbp targets two distinct fHbp variants. While many countries recommend MenB immunisation in adults considered at high risk due to underlying medical conditions or immunosuppression, there are no recommendations for routine use in the general adult population. We reviewed the burden of MenB in adults, where, while incidence rates remain low (and far lower than in young children < 5 years of age at greatest risk), a substantial proportion of MenB cases (20% or more) is now observed in the adult population; evident in Europe, Australia, and in the United States. We also reviewed immunogenicity data in adults from clinical studies conducted during MenB vaccine development and subsequent post-licensure studies. A 2-dose schedule of 4CMenB generates hSBA titres ≥ 1:4 towards all four key vaccine target antigens in up to 98-100% of subjects. For MenB-FHbp, a ≥ fourfold rise in hSBA titres against the four primary representative test strains was observed in 70-95% of recipients following a 3-dose schedule. While this suggests potential benefits for MenB immunisation if used in adult populations, data are limited (especially for adults > 50 years) and key aspects relating to duration of protection remain unclear. Although a broader adult MenB immunisation policy could provide greater protection of the adult population, additional data are required to support policy decision-making.

4CMenB sustained vaccine effectiveness against invasive meningococcal B disease and gonorrhoea at three years post program implementation

OBJECTIVES

To evaluate persistence of vaccine effectiveness (VE) and vaccine impact (VI) on invasive meningococcal B (MenB) disease and gonorrhoea at three years after implementation of a state funded 4CMenB program for infants, children, adolescents and young people in South Australia.

METHODS

VI was assessed using a Poisson or negative binomial regression model, and VE was estimated using screening and case-control methods. Chlamydia controls were used to estimate VE in the primary analysis to control potential confounding effects such as high-risk sexual behaviour associated with sexually transmitted infections.

RESULTS

During the three-year program, reductions of 63.1% (95%CI 29.0% to 80.9%) and 78.5% (95%CI 33.0% to 93.1%) in incidence of MenB disease were observed in infants and adolescents, respectively. There were no cases in infants who had received three doses of 4CMenB. Two-dose VE against MenB disease was 90.7% (95%CI 6.9% to 99.1%) for the childhood program and 83.5% (95%CI 0 to 98.2%) for the adolescent program. Two-dose VE against gonorrhoea in adolescents was 33.2% (95%CI 15.9% to 47.0%). Lower VE estimates were demonstrated after 36 months post-vaccination (23.2% (95%CI 0 to 47.5%) >36 months post-vaccination compared to 34.9% (95%CI 15.0% to 50.1%) within 6-36 months). Higher VE estimates were found after excluding patients with repeat gonorrhoea infections (37.3%, 95%CI 19.8% to 51.0%). For gonorrhoea cases co-infected with chlamydia VE was maintained (44.7% (95%CI 17.1% to 63.1%).

CONCLUSION

The third-year evaluation results show persistent vaccine effectiveness of 4CMenB against MenB disease in infants and adolescents. As this is the first ongoing program for adolescents, moderate vaccine protection against gonorrhoea with waning effectiveness three years post-vaccination was demonstrated in adolescents and young adults. The additional protection of 4CMenB vaccine against gonorrhoea, likely through cross-protection should be considered in cost-effectiveness analyses. A booster dose may need to be further evaluated and considered in adolescents due to waning protection against gonorrhoea demonstrated after 36 months post-vaccination.

Impact of COVID-19 Containment Strategies and Meningococcal Conjugate ACWY Vaccination on Meningococcal Carriage in Adolescents

OBJECTIVES

To examine if COVID-19 containment strategies were associated with reduced pharyngeal carriage of meningococci in adolescents. Also, to observe if carriage prevalence of meningococcal A, C, W and Y differed in meningococcal conjugate ACWY vaccinated and unvaccinated adolescents.

DESIGN

Repeat cross-sectional study of pharyngeal carriage.

SETTING

In 2020, recruitment commenced from February to March (pre-COVID-19) and recommenced from August to September (during COVID-19 measures) in South Australia.

PARTICIPANTS

Eligible participants were between 17 and 25 years of age and completed secondary school in South Australia in 2019.

RESULTS

A total of 1338 school leavers were enrolled in 2020, with a mean age of 18.6 years (standard deviation 0.6). Pharyngeal carriage of disease-associated meningococci was higher during the COVID-19 period compared with the pre-COVID-19 period (41/600 [6.83%] vs. 27/738 [3.66%]; adjusted odds ratio [aOR], 2.03; 95% CI: 1.22-3.39; P = 0.01). Nongroupable carriage decreased during COVID period (1.67% vs. 3.79%; aOR, 0.45; 95% CI: 0.22-0.95). Pharyngeal carriage of groups A, C, W and Y was similar among school leavers vaccinated with meningococcal conjugate ACWY (7/257 [2.72%]) compared with those unvaccinated (29/1081 [2.68%]; aOR, 0.86; 95% CI: 0.37-2.02; P = 0.73). Clonal complex 41/44 predominated in both periods.

CONCLUSIONS

Meningococcal carriage prevalence was not impacted by public health strategies to reduce severe acute respiratory syndrome coronavirus 2 transmission and is unlikely to be the mechanism for lower meningococcal disease incidence. As international travel resumes and influenza recirculates, clinicians must remain vigilant for signs and symptoms of meningococcal disease. Vaccinating people at the highest risk of invasive meningococcal disease remains crucial despite containment strategies.