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Background. Intermittent screening and treatment in pregnancy (ISTp) is a potential strategy for the control of malaria during pregnancy. However, the frequency and consequences of malaria infections missed by a rapid diagnostic test (RDT) for malaria are a concern. Methods. Primigravidae and secundigravidae who participated in the ISTp arm of a noninferiority trial in 4 West African countries were screened with an HRP2/pLDH RDT on enrollment and, in Ghana, at subsequent antenatal clinic (ANC) visits. Blood samples were examined subsequently by microscopy and by a polymerase chain reaction (PCR) assay. Results. The sensitivity of the RDT to detect peripheral blood infections confirmed by microscopy and/or PCR at enrollment ranged from 91% (95% confidence interval [CI], 88%, 94%) in Burkina Faso to 59% (95% CI, 48%, 70% in The Gambia. In Ghana, RDT sensitivity was 89% (95% CI, 85%, 92%), 83% (95% CI, 76%, 90%) and 77% (95% CI, 67%, 86%) at enrollment, second and third ANC visits respectively but only 49% (95% CI, 31%, 66%) at delivery. Screening at enrollment detected 56% of all infections detected throughout pregnancy. Seventy-five RDT negative PCR or microscopy positive infections were detected in 540 women; these were not associated with maternal anemia, placental malaria, or low birth weight. Conclusions. The sensitivity of an RDT to detect malaria in primigravidae and secundigravidae was high at enrollment in 3 of 4 countries and, in Ghana, at subsequent ANC visits. In Ghana, RDT negative malaria infections were not associated with adverse birth outcomes but missed infections were uncommon.

Serum bactericidal antibody titres that correlate with protection against invasive meningococcal disease have been characterised. However, titres that are associated with protection against acquisition of pharyngeal carriage of Neisseria meningitidis are not known. Sera were obtained from the members of a household in seven countries of the African meningitis belt in which a pharyngeal carrier of N. meningitidis had been identified during a cross-sectional survey. Serum bactericidal antibody titres at baseline were compared between individuals in the household of the carrier who became a carrier of a meningococcus of the same genogroup during six months of subsequent follow-up and household members who did not become a carrier of a meningococcus of this genogroup during this period. Serum bacterial antibody titres were significantly higher in carriers of a serogroup W or Y meningococcus at the time of recruitment than in those who were not a carrier of N. meningitidis of the same genogroup. Serum bactericidal antibody titres to a strain of N. meningitis of the same genogroup as the index cases were no different in individuals who acquired carriage with a meningococcus of the same genogroup as the index case than in those who did not become a carrier during six months of follow-up. Serum bacterial antibody titres to N. meningitidis of genogroup W or Y in the range of those acquired by natural exposure to meningococci of these genogroups, or with cross-reactive bacteria, are not associated with protection against acquisition of carriage with meningococci of either of these genogroups.

The pattern of epidemic meningococcal disease in the African meningitis belt may be influenced by the background level of population immunity but this has been measured infrequently. A standardised enzyme-linked immunosorbent assay (ELISA) for measuring meningococcal serogroup A IgG antibodies was established at five centres within the meningitis belt. Antibody concentrations were then measured in 3930 individuals stratified by age and residence from six countries. Seroprevalence by age was used in a catalytic model to determine the force of infection. Meningococcal serogroup A IgG antibody concentrations were high in each country but showed heterogeneity across the meningitis belt. The geometric mean concentration (GMC) was highest in Ghana (9.09 μg/mL [95% CI 8.29, 9.97]) and lowest in Ethiopia (1.43 μg/mL [95% CI 1.31, 1.57]) on the margins of the belt. The force of infection was lowest in Ethiopia (λ = 0.028). Variables associated with a concentration above the putative protective level of 2 μg/mL were age, urban residence and a history of recent vaccination with a meningococcal vaccine. Prior to vaccination with the serogroup A meningococcal conjugate vaccine, meningococcal serogroup A IgG antibody concentrations were high across the African meningitis belt and yet the region remained susceptible to epidemics.

[This corrects the article DOI: 10.1371/journal.pone.0147928.].

The pattern of epidemic meningococcal disease in the African meningitis belt may be influenced by the background level of population immunity but this has been measured infrequently. A standardised enzyme-linked immunosorbent assay (ELISA) for measuring meningococcal serogroup A IgG antibodies was established at five centres within the meningitis belt. Antibody concentrations were then measured in 3930 individuals stratified by age and residence from six countries. Seroprevalence by age was used in a catalytic model to determine the force of infection. Meningococcal serogroup A IgG antibody concentrations were high in each country but showed heterogeneity across the meningitis belt. The geometric mean concentration (GMC) was highest in Ghana (9.09 Mg/mL [95% CI 8.29, 9.97]) and lowest in Ethiopia (1.43 Mg/mL [95% CI 1.31, 1.57]) on the margins of the belt. The force of infection was lowest in Ethiopia ([Lambda] = 0.028). Variables associated with a concentration above the putative protective level of 2 Mg/mL were age, urban residence and a history of recent vaccination with a meningococcal vaccine. Prior to vaccination with the serogroup A meningococcal conjugate vaccine, meningococcal serogroup A IgG antibody concentrations were high across the African meningitis belt and yet the region remained susceptible to epidemics.