Seroprevalence of Bactericidal, Specific IgG Antibodies and Incidence of Meningitis Due to Group A Neisseria meningitidis by Age in Burkina Faso 2008

We investigated serological correlates of protection against Neisseria meningitidis serogroup A (NmA) in Burkina Faso before the introduction of NmA conjugate vaccine.We collected blood from a representative sample (N = 1022) of Bobo-Dioulasso residents. Sera were evaluated for serum bactericidal antibody (SBA) activity against NmA strains of immunotype L11 (F8238) and L10 (3125) and NmA-specific IgG. Seroprevalence was compared to the age-specific NmA meningitis incidence in Bobo-Dioulasso during March 2007-February 2008. Meningococcal carriage was evaluated in a subset (N = 538). Geometric mean titres (GMT)/concentrations (GMC) of SBA and NmA-specific IgG increased with age, peaking around age 20 years. Overall, 70% of our sample had NmA-specific IgG ≥2 ug/mL. Meningitis incidence was highest in those aged <6 months and 5-19 years. No NmA carriers were found. Compared to the reference strain SBA, GMTs were higher against a locally isolated strain and around 40-fold lower against Dutch strain 3125.This study provides estimates of natural immunity to NmA, according to a variety of antibody measures, which will be helpful in ascertaining antibody persistence after MenAfriVac™ introduction. Age-specific seroprevalence of reference strain SBA titres most likely reflects exposure to meningococci and consecutive reactive immunity. We could not define any serological correlate of protection

Pneumococci in the African meningitis belt: meningitis incidence and carriage prevalence in children and adults

BACKGROUND: The development of optimal vaccination strategies for pneumococcal conjugate vaccines requires serotype-specific data on disease incidence and carriage prevalence. This information is lacking for the African meningitis belt. METHODS: We conducted hospital-based surveillance of acute bacterial meningitis in an urban and rural population of Burkina Faso during 2007–09. Cerebrospinal fluid was evaluated by polymerase chain reaction for species and serotype. In 2008, nasopharyngeal swabs were obtained from a representative population sample (1 month to 39 years; N = 519) and additional oropharyngeal swabs from 145 participants. Swabs were evaluated by culture. RESULTS: Annual pneumococcal meningitis incidence rates were highest among <6-month-old (58/100,000) and 15- to 19-year-old persons (15/100,000). Annual serotype 1 incidence was around 5/100,000 in all age groups. Pneumococcal carriage prevalence in nasopharyngeal swabs was 63% among <5-year-old children and 22% among ≥5-year-old persons, but adding oropharyngeal to nasopharyngeal swabs increased the estimated carriage prevalence by 60%. Serotype 1 showed high propensity for invasive disease, particularly among persons aged ≥5 years. CONCLUSIONS: Serotype 1 causes the majority of cases with a relatively constant age-specific incidence. Pneumococcal carriage is common in all age groups including adults. Vaccination programs in this region may need to include older target age groups for optimal impact on disease burden

Age-specific serogroup-A specific IgG geometric mean concentrations (GMC) in February–March 2008 versus age-specific meningococcal serogroup A meningitis annual incidence during March 2007 through February 2008.

<p>General population of Bobo-Dioulasso, Burkina Faso.</p

Geometric mean titres (GMT) and geometric mean concentrations (GMC) of bactericidal and IgG antibody against meningococcal serogroup A.

<p>Residents of Bobo-Dioulasso, Burkina Faso (N = 941) aged 1 month to 49 years, February–March 2008.</p>*<p>For analyses with Burkina and Dutch strain, fewer sera were tested in some age groups, due to limited sample volume.</p

Distribution of serum bactericidal antibody (SBA) titres against three meningococcal serogroup A assay strains.

<p>Residents of Bobo-Dioulasso, Burkina Faso (N = 941) aged 1 month to 49 years, February–March 2008.</p

Age-specific prevalence of pneumococcal carriage, by serotype group, Bobo-Dioulasso, Burkina Faso, February 2008.

<p>Nasopharyngeal swabs were taken from all 519 participants and additional oropharyngeal swabs were taken from a subset of 145 participants aged 1 to 39 years. Serotyping based on Quellung reaction.</p><p>Prevalence percent (95% confidence interval).</p>*<p>includes serotypes 1, 4, 5, 6B, 7F, 9V, 14, 18C, 19F and 23F.</p>†<p>includes serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F.</p>‡<p>An extrapolation factor was calculated for each age group as the ratio of pneumococcal carriage at any site to pneumococcal carriage in the nasopharynx.</p>§<p>Children <12 months had only naso-pharyngeal swabs, thus no specific extrapolation factor could be calculated. We assumed the factor to be similar as in 1- to 4-year-old children.</p

Meningococcal isolates in found in nine carriers from a sample of 538 participants.

<p>– Indicates not done.</p

Age-specific serum bactericidal antibody (SBA) geometric mean titers (GMT) against three meningococcal serogroup A assay strains in February–March 2008 <i>versus</i> age-specific meningococcal serogroup A meningitis annual incidence during March 2007 through February 2008.

<p>General population of Bobo-Dioulasso, Burkina Faso.</p

Age-specific annual incidence rates of pneumococcal meningitis, by group of serotype, Bobo-Dioulasso, Burkina Faso, March 2007–February 2009.

<p>Serotyping based on PCR on CSF <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0052464#pone.0052464-NjanpopLafourcade1" target="_blank">[8]</a> or Quellung reaction on isolates (if strain isolated and stored).</p><p>Rates are expressed per 100,000 inhabitants (95% confidence interval) [number of cases].</p>*<p>includes serotypes 1, 4, 5, 6B, 7F, 9V, 14, 18C, 19F and 23F.</p>†<p>includes serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F.</p