NEW THIS FRIDAY: OPTIMAL STRATEGIES FOR MENINGITIS A VACCINATION IN THE AFRICAN MENINGITIS BELT

Wednesday, 15th of May 2013

·         IDENTIFYING OPTIMAL VACCINATION STRATEGIES FOR SEROGROUP A NEISSERIA MENINGITIDIS CONJUGATE VACCINE IN THE AFRICAN MENINGITIS BELT

• Sara Tartof mail, Amanda Cohn, Félix Tarbangdo, Mamoudou H. Djingarey, Nancy Messonnier, Thomas A. Clark, Jean Ludovic Kambou, Ryan Novak, Fabien V. K. Diomandé, Isaïe Medah, Michael L. Jackson

Abstract below; full text is at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0063605

Objective

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.

Methods

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.

Results

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.

Discussion

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.

Citation: Tartof S, Cohn A, Tarbangdo F, Djingarey MH, Messonnier N, et al. (2013) Identifying Optimal Vaccination Strategies for Serogroup A Neisseria meningitidis Conjugate Vaccine in the African Meningitis Belt. PLoS ONE 8(5): e63605. doi:10.1371/journal.pone.0063605

Editor: Ray Borrow, Health Protection Agency, United Kingdom

Received: September 17, 2012; Accepted: April 3, 2013; Published: May 9, 2013

This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

Funding: This work was funded by the Centers for Disease Control and Prevention under contract #797VE0001, Modeling Vaccination Strategies for Serogroup A Meningococcal Disease in Africa. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.