Identifying Optimal Vaccination Strategies for Serogroup A <i>Neisseria meningitidis</i> Conjugate Vaccine in the African Meningitis Belt

<div><p>Objective</p><p>The optimal long-term vaccination strategies to provide population-level protection against serogroup A Neisseria meningitidis (MenA) are unknown. We developed an age-structured mathematical model of MenA transmission, colonization, and disease in the African meningitis belt, and used this model to explore the impact of various vaccination strategies.</p><p>Methods</p><p>The model stratifies the simulated population into groups based on age, infection status, and MenA antibody levels. We defined the model parameters (such as birth and death rates, age-specific incidence rates, and age-specific duration of protection) using published data and maximum likelihood estimation. We assessed the validity of the model by comparing simulated incidence of invasive MenA and prevalence of MenA carriage to observed incidence and carriage data.</p><p>Results</p><p>The model fit well to observed age- and season-specific prevalence of carriage (mean pseudo-R2 0.84) and incidence of invasive disease (mean R2 0.89). The model is able to reproduce the observed dynamics of MenA epidemics in the African meningitis belt, including seasonal increases in incidence, with large epidemics occurring every eight to twelve years. Following a mass vaccination campaign of all persons 1–29 years of age, the most effective modeled vaccination strategy is to conduct mass vaccination campaigns every 5 years for children 1–5 years of age. Less frequent campaigns covering broader age groups would also be effective, although somewhat less so. Introducing conjugate MenA vaccine into the EPI vaccination schedule at 9 months of age results in higher predicted incidence than periodic mass campaigns.</p><p>Discussion</p><p>We have developed the first mathematical model of MenA in Africa to incorporate age structures and progressively waning protection over time. Our model accurately reproduces key features of MenA epidemiology in the African meningitis belt. This model can help policy makers consider vaccine program effectiveness when determining the feasibility and benefits of MenA vaccination strategies.</p></div

Bacterial meningitis epidemiology and return of <i>Neisseria meningitidis</i> serogroup A cases in Burkina Faso in the five years following MenAfriVac mass vaccination campaign

<div><p>Background</p><p>Historically, <i>Neisseria meningitidis</i> serogroup A (NmA) caused large meningitis epidemics in sub-Saharan Africa. In 2010, Burkina Faso became the first country to implement a national meningococcal serogroup A conjugate vaccine (MACV) campaign. We analyzed nationwide meningitis surveillance data from Burkina Faso for the 5 years following MACV introduction.</p><p>Methods</p><p>We examined Burkina Faso’s aggregate reporting and national laboratory-confirmed case-based meningitis surveillance data from 2011–2015. We calculated incidence (cases per 100,000 persons), and described reported NmA cases.</p><p>Results</p><p>In 2011–2015, Burkina Faso reported 20,389 cases of suspected meningitis. A quarter (4,503) of suspected meningitis cases with cerebrospinal fluid specimens were laboratory-confirmed as either <i>S</i>. <i>pneumoniae</i> (57%), <i>N</i>. <i>meningitidis</i> (40%), or <i>H</i>. <i>influenzae</i> (2%). Average adjusted annual national incidence of meningococcal meningitis was 3.8 (range: 2.0–10.2 annually) and was highest among infants aged <1 year (8.4). <i>N</i>. <i>meningitidis</i> serogroup W caused the majority (64%) of meningococcal meningitis among all age groups. Only six confirmed NmA cases were reported in 2011–2015. Five cases were in children who were too young (n = 2) or otherwise not vaccinated (n = 3) during the 2010 MACV mass vaccination campaign; one case had documented MACV receipt, representing the first documented MACV failure.</p><p>Conclusions</p><p>Meningococcal meningitis incidence in Burkina Faso remains relatively low following MACV introduction. However, a substantial burden remains and NmA transmission has persisted. MACV integration into routine childhood immunization programs is essential to ensure continued protection.</p></div

Aggregate and case-based meningitis surveillance data indicators, Burkina Faso, 2011–2015.

<p>Aggregate and case-based meningitis surveillance data indicators, Burkina Faso, 2011–2015.</p

Annual incidence (cases per 100,000 persons) of suspected, probable and laboratory-confirmed meningitis, Burkina Faso, 2011–2015.

<p>Annual incidence (cases per 100,000 persons) of suspected, probable and laboratory-confirmed meningitis, Burkina Faso, 2011–2015.</p

Average adjusted annual incidence of laboratory-confirmed meningitis by pathogen and age group, Burkina Faso, 2011–2015.

<p>Abbreviations: Hi, <i>H</i>. <i>influenzae</i>; NmA, <i>N</i>. <i>meningitidis</i> serogroup A; NmC, <i>N</i>. <i>meningitidis</i> serogroup C; NmW, <i>N</i>. <i>meningitidis</i> serogroup W; NmX, <i>N</i>. <i>meningitidis</i> serogroup X; NmY, <i>N</i>. <i>meningitidis</i> serogroup Y; Sp, <i>S</i>. <i>pneumoniae</i>.</p

Adjusted annual incidence of meningococcal meningitis by serogroup, Burkina Faso, 2011–2015.

<p>Abbreviations: Nm, <i>N</i>. <i>meningitidis</i>; NmA, <i>N</i>. <i>meningitidis</i> serogroup A; NmC, <i>N</i>. <i>meningitidis</i> serogroup C; NmW, <i>N</i>. <i>meningitidis</i> serogroup W; NmX, <i>N</i>. <i>meningitidis</i> serogroup X; NmY, <i>N</i>. <i>meningitidis</i> serogroup Y.</p

The meningitis belt of sub-Saharan Africa and meningococcal serogroup A conjugate vaccine (MACV) rollout, 2010–2016.

<p>The meningitis belt of sub-Saharan Africa and meningococcal serogroup A conjugate vaccine (MACV) rollout, 2010–2016.</p

Suspected, probable and laboratory-confirmed meningitis cases from case-based meningitis surveillance, Burkina Faso, 2011–2015.

<p>Suspected, probable and laboratory-confirmed meningitis cases from case-based meningitis surveillance, Burkina Faso, 2011–2015.</p

Reported <i>N</i>. <i>meningitidis</i> serogroup A cases, Burkina Faso, 2011–2015.

<p>Reported <i>N</i>. <i>meningitidis</i> serogroup A cases, Burkina Faso, 2011–2015.</p

Flow diagram of the national case-based meningitis surveillance system, Burkina Faso, 2011–2013.

<p>Abbreviation: rt-PCR, real-time polymerase chain reaction. *Specimens can be tested by multiple methods.</p