ABSTRACT
In 2002, the largest epidemic of Neisseria meningitidis serogroup W135 occurred in Burkina Faso. The highest attack rate was in children <5 years of age. We describe cases from 1 district and evaluate the performance of the Pastorex test, which had good sensitivity (84%) and specificity (89%) compared with culture or PCR.
Subject(s)
Disease Outbreaks , Meningitis, Meningococcal/epidemiology , Neisseria meningitidis, Serogroup W-135/classification , Adolescent , Adult , Age Factors , Bacteriological Techniques , Burkina Faso/epidemiology , Child , Child, Preschool , Female , Humans , Incidence , Infant , Male , Meningitis, Meningococcal/cerebrospinal fluid , Meningitis, Meningococcal/diagnosis , Neisseria meningitidis, Serogroup W-135/isolation & purification , Neisseria meningitidis, Serogroup W-135/pathogenicity , Polymerase Chain Reaction , Sensitivity and SpecificityABSTRACT
Following a large Neisseria meningitidis W135 (NmW135) epidemic in Burkina Faso (BF) during 2002, a newly licensed trivalent A/C/W135 meningococcal polysaccharide vaccine was introduced in 2003. We conducted a case-control study to assess the vaccine effectiveness (VE) against meningococcal disease. Thirty-two N. meningitidis A (NmA) and 3 NmW135 meningitis cases were enrolled and matched by age-neighborhood to 103 controls. After adjusting for confounding risk factors, VE against NmA or NmW135 was 83.6% (95% CI 31.8-97.0, p=0.01) for persons with verified vaccination. VE against probable/definite NmA alone was 94.0% (95% CI 58.7-99.0, p=0.0003). Low number of NmW135 cases did not allow estimation of VE against NmW135 alone. The vaccine was highly effective against the epidemic. Since 2003, the trivalent vaccine continues to be effectively used in Africa for the control of meningococcal disease epidemics.
Subject(s)
Meningococcal Vaccines/immunology , Neisseria meningitidis, Serogroup W-135/immunology , Polysaccharides, Bacterial/immunology , Adolescent , Adult , Antibodies, Bacterial/blood , Antibodies, Bacterial/immunology , Burkina Faso , Case-Control Studies , Child , Child, Preschool , Humans , Meningitis, Meningococcal/blood , Meningitis, Meningococcal/immunology , Meningitis, Meningococcal/prevention & control , Meningococcal Vaccines/administration & dosage , Meningococcal Vaccines/adverse effects , Population Surveillance/methods , Serum Bactericidal Test , Treatment OutcomeABSTRACT
BACKGROUND: The African meningitis belt undergoes recurrent epidemics caused by Neisseria meningitidis serogroup A. During 2002, Burkina Faso documented the first large serogroup W-135 (NmW-135) meningococcal disease epidemic. To understand the emergence of NmW-135, we investigated meningococcal carriage and immunity. METHODS: Immediately after Burkina Faso's epidemic, we conducted a cross-sectional survey of meningococcal carriage and seroprevalence in an epidemic and a nonepidemic district. We identified predictors of elevated NmW-135 serum bactericidal activity (SBA), a functional correlate of protection, using multivariate logistic regression. RESULTS: The NmW-135 carriage rate was 25.2% in the epidemic district and 3.4% in the nonepidemic district (P<.0001). Compared with residents of the nonepidemic district, those of the epidemic district had higher geometric mean titers of NmW-135 SBA (P<.0001). NmW-135 SBA titers>or=1:8, an estimated protective threshold, were observed in 60.4% and 34.0% of residents of the epidemic and nonepidemic district, respectively (P=.0002). In a multivariate model, current NmW-135 carriage, age, and residence in the epidemic district were independent predictors of having an NmW-135 SBA titer>or=1:8. CONCLUSIONS: Extensive NmW-135 carriage and transmission in the epidemic area caused residents to acquire natural immunity. Serial carriage and seroprevalence surveys could establish the duration of immunity in the population. The persistent circulation of NmW-135 underscores the potential for periodic NmW-135 epidemics in Africa.
Subject(s)
Disease Outbreaks , Meningitis, Meningococcal/epidemiology , Meningitis, Meningococcal/immunology , Meningococcal Infections/epidemiology , Meningococcal Infections/immunology , Neisseria meningitidis, Serogroup W-135/immunology , Adolescent , Adult , Age Factors , Antibodies, Bacterial/blood , Burkina Faso/epidemiology , Carrier State/microbiology , Child , Child, Preschool , Female , Geography , Humans , Logistic Models , Male , Meningitis, Meningococcal/microbiology , Meningococcal Infections/microbiology , Multivariate Analysis , Seroepidemiologic StudiesABSTRACT
Burkina Faso conducted mass measles vaccination campaigns among children aged 9 months to 4 years during December 1998 and December 1999. The 1998 campaign was limited to six cities and towns, while the 1999 campaign was nationwide. The last year of explosive measles activity in Burkina Faso was 1996. Measles surveillance data suggest that the 1998 urban campaigns did not significantly impact measles incidence. After the 1999 national campaign, the total case count decreased during 2000 and 2001. However, 68% of measles cases occurred among children aged 5 years or older who were not included in the mass vaccination strategy. During 2000 and 2001, areas with high measles incidence were characterized by low population density and presence of mobile and poor populations. Measles control strategies in Sahelian Africa must balance incomplete impact on virus circulation with cost of more aggressive strategies that include older age groups.
